stinky bathroom - makes me feel so uncordinated with the crafty!

Ok, so I was trying to re-do my bathroom, take down icky border, a 70's mirror, and upgrade it.
I painted the walls a light green, and was going to paint, with help of a stencil, a vine around the top.
However, things didn't go according to plan, of coarse.
I tested the stencil on a couple of spare cardboard peices, and it worked fine. But when I did my bathroom, it smeared, dripped, and woudn't stay taped on! Sooooooooooo anoying!!!
Any ideas for stencil? Better yet, how do you paint over dark paint with light paint?
Uhhhh.