Yes, shellac is a great barrier coat and wash coat, lacquer works well over it.

What finish can be applied over shellac?

But with that quick step on and off of my soapbox, I will say that even the company recommends that you do not use a polyurethane over shellac, but many woodworkers do this on a daily basis without any concerns. It is, however, OK to use an oil-based urethane over shellac.

Can you seal over shellac?

The problem with shellac, and part of the reason why it has fallen out of fashion as a modern wood finish, is that when used alone it is easily damaged by water and alcohol. To produce a lasting shellac finish, a transparent sealant must be put on top.