The dog brushes would work well as cards but not combs. For combing, all your really need is is a pet comb. Just take a lock of wool, comb one end and then flip the lock over and comb the other end. A regular hair comb will work too as long as you keep the locks fairly small. For the best spinning, be sure to keep your combed locks all in the same direction - tip ends to tip ends, butt ends to butt ends. If you plan to use the yarn as a singles, spin from the butt end of the locks. This will reduce the hairiness of the yarn. If you plan to ply the yarn, spin from the tip end so so the yarns are plied from the butt end. This gives a final chance to smooth down any stray hairs.