I need to prep a floor for VCT tile. I have watched flooring outfits scratch the seems with a compound but am not sure what they used. Also, I am going over 2 layers of new patchwork plywood. I had to level this floor tremendously. Most of it has atleast 1-3/4″ of flooring that is solid but i want to add a smooth layer of luan. What type of nails are best in order to not give a problem to the VCT? I was going to use a spiral 6D or Rosin coated by hand?? Or should i be using screws like i do for the thicker plywoods??

Any advise i would appreciate!!