Do you have an image of the sort of scheme you going for. Are you using an airbrush or hand brush.
If your doing the older green campo scheme, which if I am right has 3 colours, you will need something to mask the edges. For those patterns, something like Silly Putty is really useful. I use White Tac myself, but Silly putty isn't easy to get here.
I am a Norfolk man and i glory in being so
On the bench: Airfix 1/72nd Harrier GR.3/Fujimi 1/72nd Ju 87D-3