Well, I myself have been breeding frizzles for over 10 years. If you breed two frizzles together you will not get 100% curlies. You will get a few birds that have decent frizzled feathers. If you choose to do this only breed those birds over a smooth feathered bird. Preferably one carrying the frizzle gene, as it will make the offspring of this mating have better frizzles. The feathers will be wider, tighter to the body, as well as giving the bird the proper "poof" that it needs. If your just breeding them to have them then it really wont matter, but I bred them for show so I took great pride in what my birds looked like. I hope that helps you out, I had to write this while going out the door being late. If you need anything feel free to ask away.
~Casey