How can I remove dried latex paint from a bathtub and tub drain?
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
  Bon Ami.
  
  Step 6 Visit a paint company and look for "Oops". It's made to remove
  paint spots.
  
  https://www.hunker.com/13422095/how-to-remove-paint-from-a-fiberglass-bath-tub


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.