I just bought some henna samples from Mehandi. I am asking these questions in case the testing goes well and I decide to do a whole head application. Their site recommends washing/combing out/drying hair prior to applying henna.
Does it matter what shampoo I wash with? There is no way I can ever comb my hair unless it has something with lot of slip in it. Yes....even finger comb or with a wide tooth comb. My hair is very snarly.
I wouldn't want anything to interfere with the henna so what could I use so that I could comb the tangles out but not coat my hair too much?

Thanks in advance to those who take the time to respond.