Definitely, do not pay for your littera-trash. Also, do not donate for the Kingdumb Hell operations or the Worldwide Pedophile Defense Fund. That means no money is going into any of their boxes for any reason. If you get a donation from a householder, you might put that money into a regular church missionary fund, because you did promise that it was to finance a worldwide Bible educational work. (I believe that would be even more ethical, since most regular churches are doing a better job at teaching the Bible as it is than the Washtowel is.)
You could also find other ways to run up their expenses without paying for it. First, and most obvious, is never donate real money to the organization, local or otherwise. If you are only donating to the local expenses, remember that you are pushing them closer to the magic $3,000 that will trigger a bleed to the parent organization. If they threaten to cut off the lights, so be it. You could also try leaving the lights on in the Kingdumb Hell after the boasting session (so it will waste electricity), making long distance calls using their phones (preferably international) and not donating for them, and promising to bring an army to a Grand Boasting Session (to force them to locate a bigger venue) and having them not show up. This will waste more money on the rental.
Another way to make them take a bath is to pick a motel that is NOT on the "approved" list. Whatever discounts they get will be lessened, and you will probably get a better deal on your room (even if you do pay more, you will get much better quality and no bedbugs). If your a$$embly is local, do not support it in any way (no housing other delegates, no extra donations, no nothing). And yes, pick up as much littera-trash as you are allowed, without paying for it--and waste as much as possible.