Drifter, pastels very easy - recipe as follows :
1) Apply gloss / satin coat before pastelling. If base coat to matt, pastel will "grab" onto the paint resulting in a very harsh effect.
2) Use chalk pastel sticks (soft pastel)
3) Scrape pastel dust with sharp knife
4) Use old brush to gently apply to panel lines, go a bit heavier around engines.
5) Don't scrub pastel onto paint - use a soft brush.
6) Blow off excess pastel
8 ) Soften effect with large clean brush. I prefer this over a panel pin wash as aircraft very seldom show a distinct solid panel line. Many of the low visibility colours fade from dark around the panel line to nothing further into the panel - pastels allow you to do this
9) Pastels are all about subtlety - so don't use black on a light grey base for example.
10) Protect pastels with final very light matt / satin varnish depending on your desired finish.
It's as simple as that.
Pastels can be removed using lots of water and a brush but there should be no need if you approach this carefully. Work the pastel effect up. Don't go for the complete effect in one go because it'll then look overdone. Use lighter pastels on the middle of panels to give a panel fading effect.
Hope that helps