Scott,
I have used Osmo on several projects but have never tried to accelerate the drying time. I give it over night or at least several hours to cure before applying the next coat. I also do not do the "flood the surface and then wipe the excess off" that they recommend. I just put on a liberal coat and then look for dry and wet spots to even out. I like to put a small microfiber cloth in an empty osmo can and use it for each coat. I think it wastes a fair bit of finish to get another rag wet with the finish. Last, I should have ordered a bottle of nitrogen or something to squirt into the partially full Osmo finish can between projects. It is bad about curing in the can. As you know, it isn't cheap and I would prefer it not dry up on me.
I sand as I usually do. I almost always sand through 220. Seems to work fine. They recommend Osmo for a floor finish, however, I wonder if the 120 might be intended for floors. I did not realize it until I was having my oak floors redone but they seem to never sand to 150 or 220 on floors. I have to admit they look fine but then my eyes are nearly 6 feet away almost all the time.
Jim