Is it posible to post cure the mold for 4 hours? start at 50C and go up 20C every 1 hour? And then start at 70C to cure the prepreg and go up 20C every 1 hour? I guess it would work. but will it be alot of pinholes?

Depends on the tooling system used, your mould surface may suffer. Loss of gloss, imprinting of the pre-preg fibres into the mould surface, etc. Also a chance of it causing a release failure.

But, some systems it will work. Not really worth the risk in my opinion, cure the mould properly and ensure it's longevity.