Rather than do something to physically disrupt it, why not do it on the sly.
equipment needed: permanent felt tip marker, clear shelf paper from wally world, small pocket sized spray bottle with some rubbing alcohol.
Go into the bathroom right before the service starts. Spray a little alcohol into the back of the urinal to give it a quick clean so that the shelf paper sticks better. Write whatever you want on the back of the urinal with the marker. A few websites/urls, a couple quotes, etc.... Not a whole paragraph, just something small and easy to remember. Cover what you wrote with the shelf paper. The shelf paper makes it harder to remove what is written.
Quite a few people would see it before they get it removed. Someone would have to miss the entire service with their head in the pisser scraping with a razor-blade in order to remove it. If cleaned properly it is a real pain to remove. You could even wipe it down with a little silicone, vaseline, or wd40 so that if they try to scribble it out, it won't stick. Do it to every urinal in the mens room. If nothing else, whoever has to remove it will have it memorized by the time they are done.
For the stalls.......Since (at least with the guys) you are normally going to be sitting for a few minutes staring straight ahead, why not do something similar to the back of the stall door. But, instead of just a small quote or web address, print something like the UN scandal or some other article and stick it to the stall door. Whoever is sitting there WILL read it....they won't be able to ignore it.
Same for the womens room stalls except use articles or items that would be more likely to appeal to women. Maybe the pedophile issue would be a good one.
The memorial would be the best time to do this as there will be more there than just the regulars. If done to every stall they wouldn't even have the option of closing the restrooms.
Can you imagine the rumors in congregation? Even those that didn't see it would hear about it. There most definately would be a talk about how the spirtuality of the cong must be so low as to allow satans demons themselves to enter into the kh during the most holy of days, totally unchallanged by jehovah or his angels. Imagine the fear.