Thanks …. got a reply from David (myfordboy YouTube)
I always use the Precision pain on my models, without any primer. Humbrol would be fine though but go for the gloss enamel although if you are going to run on steam I don't know how that one does.
Some of my friends use car spray but that is probably more expensive than precision paints.
if you want the same colour as i used it's P125 B R Southern coach green (gloss)