My DD suFfers with the same thing on and off, its always there but flares up in an instant. I am thinking its more eczema now but had previously thought it was just dribble rash the chemist has told me the following things to try; tummy time to help dry out, barrier cream, qv bath wash, dermaveen moisturiser, if it will not get better u can try an anti fungal nappy cream (ie. Daktozin) as it can become a fungal infection.
My DD's flared up terribly the other day in the hot weather so I got a cream from the chemist which they make onsite, it does not list the ingredients so can't tell u what it is but it worked amazingly! The next day the rawness and redness had gone and she was no longer scratching at all, and that was after one application. If u or anyone else want more info PM me and I'll try find out the active ingredients.
ETA: I think vaseline or paw paw should be fine to put on it if that's what u have handy.