I've ridden in the Dually, I also hacked out in it and yes, all you do is to attach the reins to the 'training' rings.
Saff really liked it but to be honest it doesn't give the clearest of aids and though I could stop her in it (she's quite good anyway) I didn't feel I had as much control as with a Hackamore or a bit. Even our RA agrees that it's a 'rough' form of bitless.
I used it initially because Madame couldn't tolerate even the lightest of contacts. She'd come to associate a contact with discomfort or even pain. It was so bad that she would rear over a dozen times a session. I didn't have her in a severe bit, the most severe was a french link and one of my good points (I do have some

) is that I'm not heavy handed. It helped my situation and she was very happy in it but it's not something that I would use in the long term. If I was going bitless in the long term (I'm not) I would probably look at something like the Dr Cook which has very good reviews.