Mod Podge as a top coat?

Yes it works, my mom used to do this on my first bass years ago. But it yellowes pretty badly over time and is does not provides a smooth surface as other finishes does.

 

No disrespect to @Jebberz but I would avoid mod podge. I use this stuff all the time for crafting with my kids - my daughter uses it a lot. It's thin, has a weak bond, and also does not flow out nicely enough to permit a smooth finish. You'd have to do many, many coats to build up enough to sand back, and even then, the sanding process would likely tear out larger pieces of finish. A plus is that it will stick to nearly anything, but the minus is that it does not stick really well. For any of the crafts that require a glassier finish, we use epoxy, as its easier and safer than CA to get the job done with little fingers. For crafting a phony stained glass window for a dollhouse using clear plastic and tissue paper, there's nothing better than mod podge...

 

I just gotta jump in here and say I haven't heard about this product since I was in high school (or before) and my mother used if for craft projects. One of those things that brings you right back to that time. While I can't recall the smell, I'd be interested to know if I remember that, it was in my house constantly when I was a kid.