Tell us about yourself!
Pull the overflow cover off the tub (the thing the water goes down if someone tries to overfill the tub) and use any of the methods you like but applying them through the overflow. Oh and it is the gas that is produced that makes the vinegar/baking soda work - the trick is getting the baking soda to the bottom of the trap before adding vinegar - I add a small bit of hot water after the baking soda and before the vinegar to make the reaction happen where it helps. Oh - and if long hair is your problem, save yourself the headaches and get a screen trap to replace the sink/tub plug for the 90% of the time you don't want the basin to fill. Teenagers can be taught to clean the screen after every shower by giving them the joy of cleaning hair out of one drain themselves. A Mom.
Bury a disposable container so top edge is just above the soil. Fill container with beer 1-2" deep. Slugs LOVE beer...they dive in and drown. A better way to go, no?
Love the paper cup trick. An engineering degree and here I've been fishing the cord through with a plumbing snake for years. Here's to your ingenuity!