I've heard before not to use petroleum jelly products on a rash -- they seal it in too well & don't let air get through.

I get these too in the summer, particularly over the last couple of weeks we had here. I use a chamois cream, I don't think it matters which one, rip the short off as fast as possible when I am done & head for the shower. Wash the area carefully, no harsh scrubbing, then use Gold Bond medicated talcum powder on that area during the day. Avoid underwear with an elastic pantileg opening that will rub, and put on Eucerin cream at night to help it heal but allow it to breathe. That usually does the trick for me.