Experiment with it a little, I don't think you can really use too much, it doesn't build up or leave a residue. The worst it could do is leave it a little stiff if you use too much and it'll always wash out.
updated by @megan-atwood: 07/23/15 03:26:17PM
I washed them a second time today, this time it seems to have gone better. I used more shampoo and made it super lathery so that may have helped, maybe I skimped too much the first time :P here is my so far progress theyre only about a week old.