In the book "Building Your Kevlar Canoe" the author covered his male mold with drywall compound till it was spot on. Then he painted it with hot parafin. When that was smooth he went over the whole thing once more with some kind of car wax.
In the case of canoe hulls the stem areas are not closed off till later so releasing the hull from the mold is fairly straight foreward.

: That's the way I have experienced it as well. I made a fibreglass kayak quite
: some years ago at a kayak club, but couldn't stay to break it free from
: the mould. Other members did it for me. The comment they all gave was how
: easily it came out. I had spent about an hour preparing that mould
: polishing it with floor wax until it shone. I copped a fair bit of abuse
: because everyone wanted to get on with it, but the end result proved the
: point - prepare that mould well and you will be rewarded.