Coming to this late as I only found this thread yesterday, having not been online for absolute ages... then spent a long time writing a reply late last night, only to have my computer crash just as I was about to finish

… cue lots of swearing at the computer… and I had no stamina to start again, but thought I’d give in another go today.
I think both Ash and Lisa have made lots of great points about things to consider before starting with clicker. Especially as you’re dealing with quite a challenging horse, it would be helpful to really understand the theory behind clicker training and be familiar with various techniques associated with it. The rope handling as AK uses it, for example, has been an absolutely invaluable tool for me, when dealing with Jensen’s stallion behaviour, as it allows me to control him during his macho moments while keeping negative reinforcement/pressure at minimum. Go on, be a loser and read a little – we won’t tell anyone, honest.

As to using clicker for stallion behaviour specifically, there are several exercises/techniques that have helped me with Jensen. You are absolutely spot on in planning to start with the clicker outside the ridden/excitable situations. The key for me has been to get certain things, such as polite leading, back up, head lowering, yielding the hip, standing still on the mat etc so well reinforced in a calm training situation first, that it becomes almost a second nature to respond to them. In an exciting situation, you will likely need to go back several steps/lower your expectation for starters, but I have found that by doing that and then gradually asking for more again, you will quickly get the same in an exciting situation.
For me it starts with basic good manners (nothing specific to clicker training). I expect Jensen to lead perfectly – by the sound of it, so do you with your stallys. If it was me, I would still introduce clicker to the leading to get the reinforcement history, but then I’m more “purist” with the clicker than some, and like to incorporate it to everything I do. That may not be your choice, and that’s fine – you’ll know what approach will work best for you & Cseles. To me, perfect leading means that my horse will walk on when I walk on, stop when I stop, back up from the slightest suggestion, stand still when I stand still, and be focused on me, regardless of what’s going on around him - introducing the clicker into this helps to keep their focus on you. I also expect them to yield their hip and their shoulder – former so I can disengage the hip if I need to, and latter so that he will turn round stepping away from me from a light suggestion.
Head lowering has been another key behaviour to me and Jensen, as he can’t have his nose on the ground and stand on his hind legs at the same time… Again, you use it already so I don’t need to go on about how useful it is, but to add a clicker to it may mean that it will be more accessible to you, even when Cseles gets all hot about the pretty girls around him. I’ve taught Jensen to lower his head from several cues (on their own, not all at the same time lol). Like before, it comes down to a having a very strong reinforcement history. I use a hand signal, a verbal cue, activate it by sliding my hand down the rope in a certain way (using the so called t’ai chi wall – part of the rope handling I mentioned before), by placing a hand on his poll etc etc. For making the transition to ridden easier, you want at least one of your cues to be transferable to ridden – several of mine are. As you already have taught the behaviour, it will be easy for you to add cues – so just choose one that you can do both from the ground and on board, then teach it from the ground first (by giving Cseles the cue as he’s doing the behaviour, then C/T – he will make the association really fast.
AK has an exercise that she calls hip-shoulder-shoulder, and that’s another one I find very useful with challenging horses. In it’s basic, unpolished form it is a disengagement of the hip, followed by couple of steps of backing up – very useful with a highly charged horse. You will teach all the components separately, reinforcing highly and eventually it all becomes one smooth motion. I ask for it by using t’ai chi wall, one of AK’s rope handling techniques. When it’s well established and done to perfection, it becomes a smooth, engaging rein back that can be used to reset the balance – both physically and mentally.
The matwork has probably been the most useful thing of all for dealing with Jensen’s macho moments… it’s a big subject and books could be written on it (only for losers like me of course

). The CT for forwardness thread had quite a lot of discussion on matwork and in that thread, Lisa explained really well how to get started with the mat so have a look. I’ve written about how we utilise the mat in Jensen’s blog, but in a nutshell, my biggest challenge with him is going away from home – he gets very excited about all the strange horses around and can throw all sorts of colty behaviours in – screaming, rearing vertical, blaah blaah blaah, you've seen it all so know what I mean. The way I’ve utilised the mat in those situations is as follows: when his focus goes away from me and he deviates from the polite leading manners that I expect from him, I reset his focus by asking for hip-shoulder-shoulder. When he complies, he gets to go to his mat, which is a known place of high reinforcement so highly desirable. You may well find that in an excitable situation they’ll find screaming at the mares even more desirable and ignore the mat… if that happens, I go back several steps & lower my expectations. Say, at home I will expect Jensen to approach the mat dead straight, land in a middle of it, stand square etc etc – in a highly charged situation I start by accepting one hood landing anywhere on the mat, even momentarily. If he pauses at the mat, I try to throw in several click & treats at rapid succession to remind him that staying still on it is what we want. When we leave the mat, if he leaves quietly in walk, he gets to go straight back to it & reinforced highly again. If he leaves in passage shouting obscenities, I will ask for hip-shoulder-shoulder again and repeat as before. Gradually, as his randy stallion mode is replaced with his clicker mode, I can start asking for more – walking about quietly, back up, head lowering, a bit of lateral work, whatever – and also gradually start expecting the same quality of work as I would at home. If the behaviour falls apart at any time, I simply go back a step or two and build up again, more gradually. It sounds totally crazy that a highly charged stallion would re-focus his attention for the sake of standing on an old carmat for couple of treats, but it’s worked miracles for us. It used to take Jensen quite a while to settle when we went to shows or even just to visit the EC down the road, but last time out it took me all of 30 seconds to get him quiet and focussed on me & doing some really nice work in-hand – that was huge for us.
Oooops - did you say you wanted an essay? Sorrreeeee…. It’s just that “clicker with a stallion bahaviour” is a subject I deal with a quite lot so it’s hard to shut up…. though I fully appreciate that the approach I've taken with Jensen will not suit everyone, and I don't have a problem with that.