co-sign everything Korkscrew said! *high five*
I transitioned for about a year and shampooing my hair was just too harsh. I know that NOW, but back then I didn't know any better.
Ideally co-washing conditioners should have no silicones, because the only thing that can remove silicones are those harsh sulfate shampoos that our hair tends to hate. Tresemme Naturals is amazinngggggg for my hair. Read the reviews >> Tresemme Naturals Nourishing Moisture Conditioner - NaturallyCurly.com
It's cheap, it comes in a massive size and you can find it at regular supermarkets. A lot of people also use VO-5, but for my hair it's way too light.
As far as how often: It really depends on your hair. You've been transitioning for 3 months, but do you have really long relaxed hair? Or is it cut short? Do you wear it out or in braids etc? do you flat iron to make everything straight? or just do twist outs to make everything curly? The answer to these questions will determine what's practical. I'd suggest maybe twice a week as a starting point.
hope that helps! keep us updated and good luck