Yngmar has already given a good description of this task to seal the the hull deck joint. I also had trouble removing some of the very long screws with a good fit pozi bit and decent drill. A few broke and some heads were rounded, made a few holes in teak larger than I would have liked so will need to fill later.
The remaining few that had there heads rounded came our well with a later purchased screw extractor set called easy out. I was doubtful it would work with SS screws but they came out no problem, wish I had bought it before I started.
You may want to consider this if you are having trouble or are about to remove the rubbing strake/rub rail
John
