Ick...I tried it and it was a royal PITA. I was using a clear shellac, it worked pretty well until I fired the cases.
A few things happened, when the case heats up, that stuff gets all sticky (again). You can guess what happens next when they hit the ground.
After that, all that grunge from the tumbler media....care to guess?....that's right, it gets all over the case head and the only way I found to get it off was to use a wire brush wheel on a drill motor turning at slow speed.
Unless you're going to store your ammo in a really damp environment, don't worry about it, it will be fine. I recently shot up some stuff that I had loaded about 8 years ago, it was stored in the house, and it shot just fine.
To be honest, I didn't even know you could buy primer sealer, I've never seen it before (anyone care to share a link?), I know that almost all of the factory stuff is sealed, but I just thought it was some trade secret or something.