Drum Sanders, disk sanders and scrapers
When professionals need to remove a lot of wood in either a new rough floor installation, or a major refinishing where they need to get right down to bare wood, they will use the traditional drum sander, and associated disk sander for the edges, and scraper for the corners.
The drum sander is not really a DIY tool, although you can easily rent it. The problem is that it is very hard to control, and very difficult not to dig big gouges into the floor. You really need a lot of experience to do a good job, and even with experience, you will remove a lot of wood.
Square orbital sanders
The new generation of sanders, used by both professionals and DIY'ers, is a big square sander that works with an orbital operation. You put the sandpaper on the floor, a special pad on the sandpaper and the machine on top of that. There are a few tricks to getting this to work right.
This machine is not made to be used with the handle in the upright position, and those friends of mine and yours who have done an entire floor this way consider this a terrible machine to use. There is a little lever on the handle about a foot off the ground. Step on this release, and the handle drops down, and now this machine is very easy to control.
Keep moving - keep the finish cool
When you use this machine there is usually a finish already on the floor. Do not stay in any one place long enough to warm up the finish. Move quickly all over the floor, very slowly bringing the entire floor down, not one spot a time. By moving quickly, you will use the cold wood to keep the sandpaper cold, which will prevent the melting of the finish and the clogging of the very expensive sandpaper. It seems to take longer this way, but in fact it is quicker and cheaper.
A thanks to Stevenson's Tool Rental for the sanders. Always go to a rental store that will give you quick instructions in using the tool you rent. It will save you a lot of work.