Step 7Final sanding and finishing
iImage Information

I suggest hand sanding after you've got it down to the size you want. You also might want to round out the edges. I used paste wax to finish it. Some type of oil would probably also work well. I'd be careful using anything like lacquer or polyurethane because the coat might go on too thick and then it wouldn't fit your finger. Now, you should either have a beautiful ring or a useless, mangled piece of crap. If you should have a useless, mangled piece of crap, repeat steps 1-6.
Read: http://en.wikipedia.org/wiki/Portmanteau
I don't know what the best treatment is, but I would lean towards an initial treatment with light oil to penetrate it, then liberally apply silicone grease rather than wax or oil because it is more resistant to detergent, if you got any soap or dishwater/etc on your hands it is less likely to strip the grease off.
btw laquer and poly are totally different finishes so poly is not "laquerish"