Paddedfanny,
I'm double incontinent, wear a plastic-backed diaper, and plastic pants (PUL) whenever I am out of the home. AsI change at long intervals, I almost always use a zinc oxide barrier - ordinary Desitin diaper rash cream. As long as I use the barrier, I have no rashes or pre-rash irritation.

Cleaning at every change also can be significant at avoiding rashes but may not be necessary for those who do not have delicate skin. I do this more often during the warm months.
IMHO, powder is good only until you wet your diaper, after which it is no longer effective. However, for those who change after every wetting powder works fine. Many use the pleasant odor of powder to mask minor urine odor.
A lotion is not needed as a barrier if you are applying a thicker barrier cream, which is more effective for the purpose. However, if you already have skin irritation, a good lotion can be soothing to the skin
Like you, I have received different and sometimes conflicting advice from my physicians about skin care, so I fully agree with your advice about the need to experiment to find out what works best.
--John