There's a product available in this country called M.R.P. Mr Hyde masking putty, Bill used it so I thought I'd give it a try. You can get it from "Premium Hobbies". It looks expensive but you can use it over and over again. M.I.G Ammo do something that's probably the same stuff but more expensive, maybe there's more in the tin. it goes a long way.
Haddock.