Stimulating the rectal walls will cause the rectum to produce more mucus, but it really can't be used as a substitute for enough real lube. The main reason it can't is because it takes a while to get enough of the mucous to even pass as lube, and before that you're playing dry, which can cause tears and hemorrhoids much more easily than playing with enough lube.

In short: Danger, Will Robinson.

I have the burning problem as well, and the answer is to try a bunch of different lubes until you find one that you don't react to. Parabens are a very strong possibility, so make sure that you look for paraben-free lubes. I have good luck with Probe, others have good luck with carageenan-based lubes and other organic lubes. The good news is that if you e-mail the companies many will send you trial packs so you don't have to buy a bottle that winds up being unused.

Vaseline works, kind of. It's in the same boat as Crisco/vegetable shortening. Like you, I don't react to either, but as you noted cleanup is difficult (it's a bit easier with shortening I find, you can use hot water and dishwashing liquid and it's pretty fast). I'm happier with Crisco, but with both they're so heavy that they're best kept for toys that go in and stay put, such as plugs (be careful of the sheets if you use Crisco or Vaseline!). Cutting Crisco with a little coconut oil makes it better, but it's still not ideal. less