In addition to water, I've started using Brava skin cleansing wipes from Coloplast. They seem to help really clean well as well as alleviate mild irritation. Sometimes when my skin is especially irritated (due to a leak, for instance), I use some diluted white distilled vinegar and apply lightly. Sometimes two or three times, but making sure to air dry completely between applications. I get better adhesion this way than using stoma powder.
Learned this from my cousin who's a retired nurse. Though she hasn't had much experience with ostomy issues, she's certainly seen her share of infections, wounds, burns and such.