Good question Jonathan, it is really simple, no stress envolved!!. Just shellac over them, and then paint over them with the ronan primer and grisaille. After each application of paint, and while the paint is still wet, use a small pointed brush with thinner or turps and clean the eyes at that point. Don't worry about if you don't get them perfectly clean....because the next step will take care of that. After all the paint primer has been applied, and before you start painting with the tube oils, take a small x-acto knife (#1 handle) with a #11 blade and cerefully scrape away any paint that is left. Don't worry, you won't scratch the eyes, this step will clean the eye prefectly. If you have any built up paint around the eye first, take your knife and cut lightly around the eye, in case you have built up paint to remove, the "stop cut" will stop the paint that is being removed from "chipping" the dried paint on the head around the eyes. When you start painting with the oils, repeat the step with the brush to wiipe off the wet paint on the eyes before it dries. You can always lightly scrape off any dreid paint when the paint has dried, and for further cleaning at the finish, use a little lacquer thinner on a small brush....that will clear the eyes cleanly.
Hope that helps,
Keith