Howie, I've done it in the past and I was very pleased with the results. And I was all of 15 at the time.
AFAIR I just used automotive sprays but there are guys on here who are seriously clued up about the subject (Markyboy is a professional).
Long time no speak. Does this mean that the resto's on the go again?
Incidently another regular on these boards and recent near neighbour, PeterB, has a 199 sherpa with the same slimline tank as yours. Whether it's an SM I don't know.