Have just been asked by a member via pm, and I don't think this is breaking a confidence on such a message, and it was how I got my plug to the condition ready to take a mould......
I answered: getting a hull to that stage is just a lot of hard work, sanding, filling, more sanding, more filliing etc, and then once you think it's ready.....numerous (10 15 coats of) sanding sealer to harden the timber up, and then wire wool to bring it down again....finally a spray of grey primer to highlight any dents rises and other imperfections.........more filling and sanding, and then another grey primer.....if all well, a filler primer, and then rub it down with wet and dry to a (hopefully ) perfect finish, before waxing and polishing before gelcoating and laying up the mould.