Painted Wood Floors
There are inexpensive services for hire that can do the refinishing in a weekend: much more systematic and efficient than you could ever do it. In Chicago a few years ago, some of these services charged only $1 per square foot to refinish the floor.
If there are dents and divots in the floor, you should re-sand it with a giant belt sander, which will take the finish and a bit of the wood up with it. If not, you can chemically strip the finish/paint, sand it just to smooth it out, and re-finish. Every floor only has a small number of sandings in it, so you want to avoid sanding if you can.