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.