If you use a good primer it will fill the scratches. For the first coat use something like Feather fill or some other brand of primer that is catalyzed with the same catalist used for polyeter resin. Idealy these are best applied with a spray gun but they can be brushed, just expect to do a lot more sanding. For a really rough pattern 2 coats of this type of primer might be necessary but usually from there on you switch to automotive high-fill lacquer based primer applied with a spray gun.
You can avoid using a spray gun for the primer and you can even apply gel coat with a brush, but you will need one for the PVA so you might as well get one sooner rather then later so you can learn how to use it as you are learning all the other skills that go along with FRP. It dosn't need to be an expensive one, The compressor on the other hand will need to be able to keep up with it, at least for a resonable length of time.
I prefer to use a putty knife for spreading bondo unless the surface is curved more than a flexible knife will conform to. I have 1", 2", 3", 6", and 10" knives for spreading bondo. I find they have less drag and therefore leave a smoother surface than a plastic spreader. generaly speaking the less you work it the better it will turn out.
I would never use foam board for a pattern. Sure you can use it for a quick mock up to get the general shape and diminsions but I always use solid wood such as pine or poplar or 3/4" thick sheet goods such as MDF or even particle board. these materials will flex less and let you be sure you are keeping the diminisions acurate as well as keeping the pattern from twisting. It will also make it easier to add your flanges once you are ready to pull a mold.
I'm not sure where their stores in WA are located but TAP plastics has some outlets in your neck of the woods. I use their epoxy laminating resin and have bought cloth there as well. Their laminating epoxy is basicly the same as West System 3. They don't have the biggest selection of cloth but for most of what you might want to do they have something that will work and you won't have to pay hazmat fees or wait for the brown truck. They also have small containers of cab-o-sil, microspheres, and talc so you don't have to buy huge bags of those materials.
redprimo screwed with this post 09-23-2012 at 12:30 PM