Not a good idea to put thinner on the floor for any reason. It will not keep paper from clogging. Who told you 12 grit and why?
Are you doing this yourself and what type of equipment have you decided to use?
Drum sanders are the fastest but will not get near the edges and you can do a lot of damage in just a few seconds. Orbital floor sanders work slower but are much easier for diyers. They will take more paper in successively finer grits but you would have to try to screw up a floor. They will get up to the edges.
You should get a floor sanding book or two from the library or from Amazon or something and familiarize yourself with what to expect before you start. If you have a lot to do, you may find it cheaper to bring someone in to at least do the sanding. Be patient though, good floor people stay busy and have waiting lists. You don't want the bad hacks in your house.
I agree with the use of the orbital sander, much easier to control. I sanded my LR and DR floors, they turned out beautiful but my 1 regret was that I was in a hurry and wished I had put at least 4 layers of finish on, also I would suggest using the proper applicator or your finish will have small bubbles in it. A Great website with a how to is hometime.com