I think Plastidip is a bad idea, since it would add thickness, and not be durable especially on the dropouts etc. It is still an intriguing idea.

For self-painting, I haven't done it, but I have also heard that preparation is essential.

I know there are some threads on the topic on this site, you may want to take a look at Classic & Vintage... I recall seeing a few relevant threads there over the past several years.