A few old English methods: the classic Silvers pads were glazed with a very hot blade which just melts the surface, tricky if you are not experienced.
The other way is to apply one of a variety of varnish. Best in my experience is proprietory french polish which you apply in a few light coats. It does wear off but you can just slap on another coat or two. Also it can be removed very easily with a little solvent.
Acrilic varnish works well but make sure you have a flexible one or it will just crack and flake off.
