I found that I can rent a floor sander and buy the sand paper to lightly "screen" our hardwood floors. What grit is best? Then what? The old floor is in pretty good shape but there were two floor furnaces which we removed and had patched so those areas will need more sanding and a very light stain. Some people have said "recoat". The floors were put in in the 30's and I don't think they have been redone. Suggestions please.