Diaper Rash Care

Ive been using diapers for a while now and ive messed in them a few times. I have always gotten even a minor rash at minimum and just recently got a rash from just pee so I am wondering how to prevent this or at least help it not be so bad.

I am trying to do some rash cream but am not having luck with it. I dont know how and where to put it on or how much and not much comes out so its really light. Then I use some baby powder and odor control powder.