Do it as often as you feel like your hair needs it. I suggest using a very light conditioner for co-washing, followed by a deep conditioner. You will have to do some experimenting! Good luck!
-3a/3b, fine, very thick, normal por., normal elast., long, dye- free (CG since Nov. '11)
-CO: every other night (air dry) VO5 (various scents)
-Low poo (1 or 2 times a week as needed): ION Color Defense Clarifying or Giovanni TTTT
-RO: GVP CB
-LI: Giovanni DLI or a tiny bit of VO5 (my co wash)
-Styling: BYZ Noodle Head Tame your Curls Mousse
-PT: ION Effective Care