1) Wash baby's bum with warm water; add some hand soap if you'd like and PAT try (don't rub)
2) Give baby a few minutes of "naked bum time" on the changing table or on a towel on the floor as often as possible after said wash
3) Use aquaphor LIBERALLY when a diaper is on
4) For poop diapers, we used water wipes and bought them at Target (since some of the Amazon ones had mixed reviews due to suspected counterfeit items)
5) Baths are good, but do not scrub the area
6) Usually there's a solid cause like stomach acid changes due to teething, antibiotics, or a food allergy. Also, factors that increase BMs can cause diaper rash (e.g. added fruit in diet, increased eating due to growth spurt, etc.)
Good luck OP!