When my baby has heat rash, I let her go topless, just diapers (no aircon, fan blow away) without applying anything. I usually let her sleep till she wakes up then wipe down, apply lotion (cetaphil baby), slightly let it dry then apply Sudocrem on top. Wear holey singlets or cooling tops. I’m not a fan of steroids cream so even thou I was prescribed steroids, I didn’t use. Steroids often clears when applied but comes back once stops so no point IMO. At night I will just wipe down, apply the above then wear pj. No pillows/blankets.
Ahhh my baby also same! Until his onesie and swaddle is damp or wet at the back(not pee). He also have rashed but i dont do anything with it. During daytime or even night time i always use singlet or those eyelet tops, with holes. Even with that his body will feel warm