I am going to help my brother in law refinish his front porch this weekend.  I am not sure of the material (he lives 4 hours away, and he probably could not tell the difference between pine and sheet rock)  I do know that it is a wide plank tongue and groove material,  Before speaking to me or anyone else he tried to power wash the finish off last weekend which did not work.  I am assuming we will rent a sander, remove the finish and install a new finish.  The porch is five years old and some spots the finish is completely gone,  Will an orbital sander work to remove the finish, or will we need a drum sander?  What would be the best sealer product we can get?  He lives in Verbank New York