Is there a preferred way to handle diaper rash in adults?

Same: Same as a child. Desitin (zinc oxide diaper cream) ointment, corn starch or baby powder for mild cases. Keep the area dry and clean. If no improvement, see a skin doctor.

Adult diaper rash: For adult “diaper” rash keep skin clean & dry. Change diaper as soon as it's soiled or wet. For healing go without diaper for periods of time so affected area can air out. Avoid tight diapers or airtight covers over diaper. Meds your Dr. might recommend include antifungal cream (for fungus), a steroid cream (for significant inflammation) or an antibiotic (for bacterial infection.)