When I started with daily co-washes, my breakage increased. After studying and working with my hair, here's what I found:
1) No manipulation WHATSOEVER if you're going to daily co-wash. I basically apply a leave-in, cover with a silk scarf. Then in the morning or if I have to go out, I wear a wig. You may be able to get away with Braid-outs & such.
2) Must include protein. From what I gather, protein holds the bonds of your hair together and when that bond has weakened, breakage occurs. So, I have to include a light protein treatment 1ce or 2ce a week. Light protein for me = ORS Hair Mayo or Aveda Damage Remedy.
3) KISS, dahling! Minimize the number and quantity of products you load into your hair after you co-wash. Loading tons of products weighs down your strands and may cause breakage. Just think how easy it is for your comb to snap your strands when your strands are weighed down.
4) Don't forget to clarify 1ce/month or more often if you have hard water. When my breakage increases, I clarify and do a protein & moisturizing DC.
That's all I can think of now. Remember, these were my experiences and now I have very little to no breakage when I co-wash daily. BTW, i have fine hair so you might want to take that into consideration.