Rash on my son.Please help?

My son has developed yet another rash. He is prone to diaper rashes and has had a few heat rashes or viral rashes with colds. This one feels different. It kinda feels sand papery to an extent. His doctor is out of the office,and due to bad information the one time he saw the NP I refuse to take him back there when it is only her who is there. I wasn't sure if this warranted a trip to the hospital as it doesn't seem to bother him much. He scratches at it every once in a while but not nearly enough for me to think it is something like measles or anything related to that. I thought it was a heat rash but the last time he had it,it didn't feel like this.Last time there were a few bumpy areas (like pimples) and other areas were smooth but you could see the red spots. This one feels like extremely dry skin mixed with sandpaper in spots.It looks like the Prickly Heat Rash,but it just feels different. It's all over his face and his arms but really nowhere else.He has a few stray bumps here and there on his legs but his entire face/head and arms are covered with it. All in all,Monday I'm taking him to see his Doctor but until then is there anything I could possibly put on it to make it decrease?? As I said he does not seem uncomfortable at all,except for the rare occasion he ends up scratching at it,nothing oozes from them and there is no crusting or anything like that. I think it is heat rash considering it's been nearly 100 for the past week and our AC unit broke 2 days ago.I've been taking him to the store with me and playing outside in the water or put him in a cool bath to keep him cooled off,and the fans keep it relatively decent inside the house until the guy gets here to fix the unit. Thanks for any advice.