Are you using cloth dipes at all? It can be tough to get the yeast out of the dipes and a relapse is pretty common if the dipes haven't been seriously sanitized.
Other than that... are you sure it's yeast? Some diaper rashes (like Impetigo) need different treatments or even abx.
This Dr Sears page has some good info on that.
Sun on the bum is good, you can sprinkle probiotic powder on your nipples before breastfeeding and some mamas sprinkle it on the bum as well (there are vegan/non dairy probiotics just for infants), rinsing the bum and patting/blowing dry with each diaper change, checking your diet for possible allergens, etc... they can all help. Oh, and you may want to try something like the diaper rash soap by Earth Mama Angel Baby... my dd2 gets bad rashes (sometimes bleeding) but hates pastes. So we use the soap, calendula and "skin scrape soothing" oils, and the really "light" diaper creams if she'll let us.
But if nothing seems to help and a long trip looms, maybe check with your care provider just to see what can be done to make your little one more comfy?