[Chuck Moreland]

I've done 5 floors myself. Do a search online, you will find useful 'how to'.

I've used belt and drum sanders. The vibrating type I've used are a waist of time, not aggressive enough - perhaps useful only for removing finish on a really smooth floor.

Keeping the sander moving is key. You need to have the sander moving before it touches the floor, and keep it moving as you lift it off the floor. Never back-and-forth without lifting. You need to feather the cuts on/off the floor.

You also need to select the proper grit for the amount of material you are removing. Err on the side of finer grit to slow the removal till you get a feel for it.

Cutting cross grain is most aggressive, followed by diagonal, then finally with the grain.
Which direction(s) you cut depends how much material you need to remove.

With a typical floor that needs some smoothing you might start with diagonal passes (alternating direction each pass to cross-hatch), followed by final passes with the grain, progressing to finer grits as you go.

Rent an edge-sander for the walls. Also have a hand-held oscillating sander and maybe a detail sander for getting into tight areas.

You should be able to complete the sanding of a typical room in an afternoon.

It's important to have the right equipment, but the results depend on you and how careful/skilled you are. Having done 5, I still can't get the look the good pros achieve. But my results are plenty good and better than some pro jobs I've seen. Plus have actually done it, my eye is more critical than average.