Hi Ladies, yes you absolutely can use Body Art Quality Henna immediately after relaxing. I recommend putting a plastic cap over your hair and doing a strand test first if this is your first time using henna.
Also when I do mine I put the conditioner on and a heat cap, and let it sit for a while. I have not gotten hard or dry hair from henna but once and I had not rinsed it all out that time.
As far a conditioners go, on my last henna job I mixed the Cholesterol/olive oil conditioner and Fermodyl into my henna mix. I had run out of pectin and did not have any yogurt in the fridge. It worked beautiully. I ould still recommnend a deep moisturizing conditioner though, because that is protien on top of henna. It makes the hair extremely strong.
HTH
Softresses