As a dog groomer myself, I would have to say that the best thing to use would be groom bands. Them don't slip out and can easily be pulled out with a comb. I don't use the metal clips anymore because once a tried to put them in a dogs hair and she ended up getting if off and swallowed it and had to be taken to the vet.
I'm sure if you were to make up a bunch of simple one or two color grosgrain bows, and took them around to the groom shops in you area the groomers would buy them up. Because let me tell you there is nothing worse then having 15 dogs to groom and then trying to make bows too(:
Just a tip. If you go to the dollar store and buy multiple packs of these: http://www.google.com/imgres?imgurl=...iw=981&bih=632
And cut them off the bands and just attch one to each bow, they will sell for 10 times as much.