I scuffed the matting surfaces of the flat pieces as well as the angle pieces. I did not scuff the surfaces that will ultimately have to be wiped down and re-primed when I paint the plane (at that point, I'll wipe the primer off with acetone, then scuff for the paint primer). I just used self-etch rattle can primer (Rustoleum) for all of this. I like it a lot better than the other rattle can stuff I had, but my guess is it's not very tough, at least compared to the Stewart primer. Good enough for two surfaces that just get sandwiched together and will never see wear though.
Once the primer dried, I riveted the brackets together. I did the brackets for both wings.
