I can tell you how I would approach it, and have previously. I am assuming you are going to going over the existing the OSB directly, and not put down some 1/4" underlayment. First, I would rent a floor sander/buffer (Home Depot rents them.) and buy a few 80 grit sanding discs. Then sand the entire floor. I would use sixteen 7/8 " staples every square foot to prevent any future movement of the OSB, you could also use roofing nails or drywall screws, but both can get pretty tiring. When you are finished stapling/nailing whichever, using a 6" or 8" flexible mudding knife, feel for any staples that are protruding above the surface and hammer them down. You will be surprised how many were not driven down completely. I would now skim coat the entire floor with a cement based underlayment like Mapei Ultra Skim-Coat or Ardex Feather Finish, using at least a 12" trowel. When that is dry you could sand it using the rented buffer and some fine grit paper using fast breaths back and forth over the surface. But, I think scraping down the the ridges, left from the trowel, using a 6" scraper will suffice. Now as far as using adhesive as a leveler, I could not recommend strongly enough against it. That is a lot of glue on the floor and will take days if not weeks to cure and when it does, it will be too resilient. Furthermore that much glue will just make a big mess, remember the reason for using a notched trowel to spread glue is to not leave that much behind, a lot goes along way. Speaking of adhesive a 1/32" trowel will do the trick, and make sure to use firm pressure. I learned this as an apprentice, the journeyman do not like it when there are puddles of glue left on the floor, it will always seep through the seams and you have to hear about it over lunch.
John
