I find that I can distribute gel easiest when my hair is dripping wet right after my shower. I rake a little gel into my top layer (but try to finger comb each section only once or my hair starts getting stringy), then flip my head over and scrunch more gel in. I usually don't have problems with missing spots then.
Maybe I'm way off (since I haven't tried it), but I think that if I brushed my hair, and then applied product, the brushing would have seperated all my hairs so it's harder to cover all of them. I'm not sure that makes sense, but it's a thought. Have you tried instead to not brush, and apply products while combing with a wide tooth comb? Why do you brush? To get tangles out?
3a/b, fine hair... with a mind of its own!
Your hair, it's everywhere. Screaming infidelities, taking its wear.