When I was a child it was very clear what I was allowed to see and what I was not allowed to see and there was no discussion or option or negotiation. Whatever my mom said that's what went down.
It's to paint directly on the canvas without any funny business as it were and I use almost pure turpentine to start with adding oil as I go along until the medium becomes pure oil. I use as little oil as I can possibly help and that's my method.