Hi all, 

I have a question regarding making moulds from mdf or oak. I cnc milled 2 moulds, one from MDF and one from oak. Moulds are for bike helmet I want to make.
Can you recommend what final layers should I put on mould? What couloring or something like that?

I already tried to put some colors but mould got ruined because carbon with epoxy resin glued to it.

Please any help and I will be grateful.

I agree with Lester.  You need to seal the wood before you can do anything.  You can release off a primer surface or even well resin-coated wood but it still takes some work.  MDF will work fine for composites molds provided you don't expect too much.  Oak may crack in thick sections and be unstable because of the grain - but I've never tried it!  

Here's an article I wrote about using MDF for molds:  https://explorecomposites.com/articles/tooling/using-mdf-for-composites-tooling/