Paul,
First of all welcome back to the best hobby outthere and hope to see you around here on FSM in the future!
What did you use to paint the plane and glosscoat and what have you used to make the washes? If it won't come off (easily) it might be that your wash is too agressive (enamel based wash on an enamel based glosscoat is usually a bad idea for instance) or the paint coating is too "gritty". You really like to have a baby butt smooth coating of future so the wash runs in the panels nicely and wiping it off is easy.
As another cheap but very effective way to make washes is to use watercolors. Experimenting with the technique for the first time i wanted something that was fully waterbased so it would be easy to handle. At a local craft store i found a box of tubed watercolors in all the major colors for just about 3 bucks. Will last you a long time
Blob of paint in a cup....good splash of water and a tiny drop of dishwashing agent or shampoo and you are good to go! Will wipe off nicely with a q-tip treated with water or saliva. For some weird reason i always have better results with saliva.....
Hope this helps!
Richard