M.R.
I use Aquaphor as a barrier which REALLY helps and I even use it when my son doesn't have a rash. I also use Aveno diaper rash cream which is the BEST I have ever found and his rash was gone in 1 day.
Air dry helps a lot as well.
Good Luck.
Since I have been putting Aquaphor on his bottom every day since he was 7 months old he has only had 1 or 2 VERY mild diaper rashes.