It is notoriously difficult to roll down a depleted henna cone with only one hand. And it's just hard to get all the angles of your hand without smudging something.
I did a "trial run" of a pattern I created for my wedding. I'm sure I'd like it better if someone else had applied it. Some of my lines are too thick and I have somesplotches and smudges from where the sealant didn't dry all the way before I wrapped it up for bed. Overall it's tolerable, but it looks far sloppier than I want for the wedding. I think I'm just going to borrow a henna-experienced friend to do it after I sketch the outlines with aquarellable pencil.
I'm pretty sure my paste is too old for super-dark stains. Gonna have to mix up a new batch before I can play with henna again. The back of my hand and my inner wrist/arm are a lightish red-brown. My palm is a decent cherry wood color at the end of the first day, though.
Here's the pattern (paste-on; I don't have a stain photo yet)