If the pressure washer did not remove the anti-fouling
paint then it is probably not going to come off anytime soon.
Bottom paint does not need a primer but the surface you apply it to does need to be clean, dry and scruffed up with some 3M pads or some sandpaper.
Look carefully for blisters
on the bare spots...especially near the waterline. Hopefully you will not have any.
There are two types of bottom paint..paint that ablates meaning it is designed to fall off over time exposing new anti-fouling
agent and there is the harder bottom paint which is designed to remain very smooth. The latter is more appropriate for racing
boats which don't mind sending a diver down frequently to clean a bottom which fouls at a higher rate.
It's okay if your bottom paint comes off easily if it was an ablative paint in the first place...this is normal.
If you feel the need to knock off excessively loose paint then get one of those very course scrub pads on a pole and wet sand down the loose stuff. In fact, do this anyway to assure a good surface for the new coat.
You can do this now and then apply a fresh coat in the spring.
Most people choose to roll on the paint which is cheaper but it also means the paint may not have been rolled on evenly leaving an occasional thin spot that has ablated to the point where there is no paint left.
If you want to spend the bucks, then you could have all the paint removed, the hull
sprayed with an epoxy
barrier coat like Interlux
2000 or Interlux
3000 and then have a bottom paint sprayed on. But since you are not racing
, I would not bother.
Since you cannot get TBT anymore, look for a copper based paint. The higher the percentage of copper the better. Try not to go into shock when a gallon of copper bottom cost you over $150.
There are paints now which are not supposed to hurt marine
life but from what I have seen they are not anywhere as effective as copper based paint. Nobody has found a clearly effective solution yet.
Another wise idea while you are hauled out...pull all your thru-hull valves and inspect them.