I almost always precoat and then fill. If you did a really good job most of the small cracks and holes will be filled by the precoat. Any remaining cracks and holes I fill with a wood flour, flour, cabosil, whatever it take/epoxy mixture to match for color. I do this to avoid splotches. I really never quit trying new and different ways to get this job done. After filling any cracks and holes I usually end up sanding the hull, or deck, but not down to bare wood. Only to smooth the fills and match for color. Then I'm ready to wet out the fiberglass.