Late to this thread, but we use the Costco paper. We did the test with 1/4 cup water in a jar, add one sheet of paper, shake for 15 seconds, and see if it breaks apart. I'm sure most of you already know this, I just learned it this past year. The Costco paper liquefied, just like the RV paper did (tested both). I agree lots of water is probably a top 5 in keeping the black tank clean, but I think a thorough cleaning each trip with some type of tank jet system is also a must to stop buildup.
We take our cats camping (long story, but they're indoor only) and I made a critical mistake that caused a huge odor problem. My wife loves our cats more than she loves me, I'm fairly certain, so we have a corn based clumping litter, not clay. At home we flush this down the toilet into the septic tank and have not had any issues in 13 years (pumped twice already, all OK). However, in the trailer it became a huge odor problem and I think it began to ferment, or something. Now our previous 5th wheel was a Laredo, so maybe the venting system wasn't as good, but even on a 1 week camping trip it became an issue.
It took multiple tank flushes before I could get it to run clear (after getting a Rhino clear 45 degree adapter), and we've never put that litter down the trailer toilet since. I also thoroughly flush the tank after each trip. Long and short, don't put anything down the toilet that didn't come from you or the toilet roll!
The only reason I mentioned this is that although the litter took time to clear, there was no sign of toilet paper. I also learned from the shake test that Kleenex doesn't break up, so put it in the garbage can. On the new Monte, I plan to continue to use Costco (good quality and inexpensive) TP, use regular flushing, and monitor the dump to make sure it's running clear.
I also like the macerators that attach to the tank outlet, but I would prefer it if there was a way to make that a permanent install, instead of putting it inline each time.
Is it appropriate to ask what type of sewer hose people prefer, or should I start a new thread?
Mark