There are a lot of finishes you can use. For years, I used polyurethane, which works, but it yellows. Then I used Crystal Clear for a while and then regular Lacquer (9-10 coats). Finally (recently) I started using a two part epoxy. That pretty much requires you to make some sort of turner that rotates the call slowly until the epoxy sets, although, I know some guys that don't use one.
There are many ways to skin a cat!