I asked around and didn't find much. People always told me to do a full respray. If I had the original decals, Mercian (for example) close by and could afford it I would have done it. As it was I just tried to remove the rust and disguise the "bruises". I'm afraid I just improvised with the tools I had at hand.
sanding, grade of paper etc
any product used to treat the rust
prime the paint
Here it goes:
Removed the rust with 1000 sand paper.
Didn't use any product to treat the rust.
Didn't prime the paint.
Used two yellows, one ocre and white enamel to get the right shade of paint.
Waited two days and leveled/sanded/polished the paint with 4000, 6000 and 8000 micro mesh sanding sheets.
Repeat the paint and level steps until satisfied with result and done.
always glad to see this thread come back. we'll i've dug out my old steel and i'm contemplating the above