I am getting ready to re-finish the floors in my house that was built in 1940. The floors are the old tongue and groove pine solid wood floors. I am wondering what the best step by step course of action would be. I am ofcourse going to sand off all of the old finish before applying any new material. Since it is sucha large area I am not really wanting to scuff up the polyurethane imbetween coats, is there a product that is specially made for floors that you do not have to do this on, or is there an easy way to do this? Any help will be appreciated!! Thanks guys!