You can apply bottom paint
with all three methods. Spraying comes out the smoothest. Using a roller with a shallow nap comes out pretty decent. Brushing on of course is the crudest method but is fine for small places that need a touchup....like where the support pads were. Brush parallel to the water
I would not get too picky about how smooth the bottom paint comes out unless you are racing
. We are only talking a few one hundredths of a knot
difference between a spray job or a good job with a roller. I have seen people go back and wet sand the finish coat to knock down the high spots but I think that is a little obsessive. What can I say, they were racers.
As far as reducing (thinning) goes, check the label on the can. If you can reduce the paint at all, it must be done using the manufacturers specified reducer. If the label does not have enough information then call the manufacturers help number.