What if I had a bow that someone had sanded down the glass some on the back, to put skins on I assume, could I cover that up with some poly or tru oil and still make the finish look good?

Poly will def work on glass, but it may not with the rest of the finish. It softens some laquers.

Think Tru Oil will be a better choice?

I'm not sure what tru-oil does with other finishes.

Most likely you will be ok, but just warning, I have sprayed auto clearcoat on a rosewood riser, and to take the shine off, followed with spar urethane satin.  It got gummy and wouldn't dry at all...

Tru-Oil is a great finish. but it will yellow light colored glass.

Thanks guys ill try Tru oil and we'll see what that does