I use this stuff on dry hair? It's only my second time using it and I forgot that I'm supposed to wet/wash my hair before putting it on 
Also, do you always leave it on overnight or do you some times just do the 1-2 hours per the instructions? What's the longest you've left it on?

Also, do you always leave it on overnight or do you some times just do the 1-2 hours per the instructions? What's the longest you've left it on?