If you oil it, the polyurethane won't stick. Like trying to paint butter. The linseed oil never dries. Watco will dry, but I don't know if you can coat it. You have to talk to someone that's familiar with the wood in your drum, to find out the effects of the finish choices. You may have to do the same thing to the inside as you do to the outside in order to make the wood move evenly during changes in moisture content.
