It was a couple of years ago and I'm trying to remember....It wasn't easy.
The paint is from a local costume shop with clown make-up, and if I recall correctly it was the biggest cake of green clown make-up I could get my hands on. It was water based, not grease paint.
I used a big make-up pad, like you use to put on powder foundation, wet the pad, loaded it with green and PATTED the make-up all over. Same thing with any kind of oil based make-up, you have to pat it on, not rub. Rubbing is what causes the streaks and lifts it off so it gets patchy. Use a lot of the paint, too. When you're done, go over everything with translucent powder to keep it all on (for a while, anyway...eventually everything sweats off).
The thing I remember about this water based stuff was that when it dried, it kept turning into powder that would just fall off, so I had to use a lot over and over. I was terrified I was gonna bump up against someone and leave green marks everywhere...but, somehow it all pulled through.
I hope that's helpful. What's the black for? I did a dark elf as a teenager that was a disaster!