Bryan,
Have you watched Kerry Fores's video about Nuvite polishing on the factory website? It helped me a lot when I first started polishing. I believe the basic recommendation would be one light "fingerprint" of polish for every 6" X 6" area to start. If you've used 1/2 lb already you may be using too much (the stuff really seems to work well on a "less is more" approach). I use the Harbor Freight el-cheapo orbital polisher, and 1400-1500 rpm seems to be a good speed with light to medium pressure on the skins. I tried running it a lot faster but I don't think it works as well.
Of course, this also depends on how many passes you're doing per area. I just started polishing the tops of my new wing skins and after 3 passes of F9 things are looking good, but I may do 1 or 2 more passes before going onto the C grade.
It's just my opinion but to really get a nice, highly polished finish, expect 4-6 passes of F9, 2-3 of C, and 1-2 of S.
For someone starting off and wanting to polish the whole airplane, I recommend 2 lbs F9, 1 lb C, and 1/2 lb S. Just my two cents though!!