I'd have suggested Goof-off or Oops, which are for latex cleanup. Here's a more robust plan.
Step 1 Scrape paint off the fiberglass tub carefully with a plastic
scraper. Clean with Barkeeper's Friend and water. Rinse thoroughly and
repeat if necessary.
Step 2 Try Dirtex in a spray can to remove latex
paint from a fiberglass tub. It's available from ACE hardware stores.
Step 3 Make a paste of baking soda and water. Rub the paint spot with
the paste and a damp sponge. Rinse completely.
Step 4 Rub the spot of paint with a dampened Mr. Clean Magic Eraser.
Step 5 Scrub the paint spot with a non-abrasive powdered cleaner like
Step 6 Visit a paint company and look for "Oops". It's made to remove
As for the trap, you may want to remove and discard it. parts are cheap. If it's not accessible, try the products mentioned above to dissolve it, or go to more aggressive drain cleaners. Be aware that they will remove chrome from your drain hardware.