Aloe vera gel. The stuff you slop on your skin when you have a sunburn.
Especially the cooling kind that has a little menthol in it, and if you luck into finding Solarcaine Aloe Vera Gel with lidocaine in it, well, happy bum!!
Just put some on loo roll. Loads better than baby wipes or wet toilet paper.
It's water soluble so no oily residue like cream or baby oil, kind to your skin, glides easily (very very important for an ouchy bottom) and not expensive. And soooooooooooooothing...
There, I just had to share, because I know I'm not the only one who cried after the first bowel movement post-birth, and my h'roids and other bum issues have made me cry plenty.