I like to make a shallow recess in the bait with a brad point bit. This recess creates a little dam that is in a perfect circle that holds my base coat into shape. I do have to build up paint or use a simple filler to fill the brad point hole. the base coat is usually thin and i use a small wire to insure that it gets to the edges. I use a 10/0 brush.
I like to use a black fingernail polish for the pupil because it will mound up to help the 3D effect. It sometimes takes two coats to build the mound. After it dries a small drop of 5 minute epoxy is placed on the eye, again the recess helps contain the glue in the shape of the eye. That is the part that gets a bit tricky.