I don't know if it is normal, but I do something like this. I pray, or set intention that I will have a renewed mind, heart, body and spirit. I imagine myself being washed clean from whatever negativity has built up so that I can start again fresh. I don't envision my skull being washed per say. It is more a state of being I'm trying to achieve.

Welcome. Happy to have you here. I hope you find the answers you are searching for.