Jess

I use wax all the time for stuff that's not going to cure in the oven. 3 coats, no PVA. I use semi permanents only for prepreg work, they are way too expensive and a waste when not used to their full potential. Don't get me wrong, they work perfectly for this, but its over engineered. If you were using epoxy gelcoat and vac bagging, maybe.

So you would suggest not to use chemical release agent, but only wax because it protects the part and allow to demold as well ?

I would use wax to make the mould. Wax fills in little scratches and imperfections. A semi permanent is almost too good at reproducing the surface and will transfer all these imperfections to the mould. Also, wax release will smooth out the yellow wax you use to seal the trim line.