Have you tried the Uniball Posca pens Vince? I have a set & I'd recommend them to anyone, they're almost like a paint rather than ink. They're also washable whilst wet so screw ups can be easily reworked.
I have a little powder coating system in my man cave which is so simple & easy to use, but with pro looking results!
The initial set up was expensive mind!
It's better to have it & not need it, than to need it & not have it!