I just picked up a High Hand and it looks to be in a similar condition that yours was.
Therefore, I'll be going back over the thread again now that it's more relevant to me :)

Quick question on the air brush paint.
I have tried using the createx opaque range but find that I have to do a lot of coats to get good coverage and I get a noticeable edge after I remove the mask.
Also the colour doesn't really cover darken areas that well. Do you put down a white base first or is it that the paint I'm using doesn't provide a solid enough colour?
I'm new to air brushing so sorry if it's a basic question

"Noticeable edge" means you are using too much paint.You should only use enough paint to give that area the colour you want. If you HAVE to use a lot of paint, then I would change to a better paint supplier. I use Jo Sonja's range, and they are not the "top shelf", but they do the job and are easy to work with.

For any given area, I have one "mist" coat, then a max of three, even and consistent coats. Doing that "extra coat" for playfield work is not necessary at all, and will creat the edge you speak of. Also, NEVER go with a heavy coat. Always go with thin coats.