Epoxy Parfilm Pintable Release Agent in a 12oz aerosol can. Instead of using silicone based release agents, try Price Diriscoll Epoxy Parfilm. Primarily for use with epoxies, this will also function with other resins. Being silicone free, after washing your cast painting should be no problem as there are no Silicones present to cause fish eyes or bond problems.
The material places a very thin film on the mould surface which will help prolong the life of the mould whilst mainting the fine details.