How do you refinishing old hollow core interior doors?
It depends if you are wanting to stain or merely paint a door. If you want to stain it, you need to strip it to bare wood with chemicals. If painting you need to sand the entire surface only enough to rough the surface so the new paint will adhere. If you are changing the stain and finish, after you remove all the old stain wait a couple hours before you restain. Then apply a coat of polyureathane or lacquer to seal it.