OK..to apply the KISS principle..

Just go to a Home Depot, or whatever, Auto Accessories section..tell the guy/girl that all you want to do is paint out the chrome trim on your car..badges, trim etc...( they'll NEVER understand the accordion flapper story..!! )

If they're half decent salespersons..you'll walk away with a can of grey primer( hopefully etch primer which has a small acid component in it which bites into the metal and provides a key ),a can of finish coat to your colour/finish selection , and possibly a can of clear coat .
Before you apply the primer clean the rods with a little solvent...mineral turpentine, etc. to remove any fatty deposits off of your fingers etc.

And..paint it outside or in a workshop...allow for spray drift onto adjacent items..particularly your accordion...cover it totally.

Also..try a bit of your painting on a steel rod first.

That's it..can't tell ya any more.

That's a lot, thanks Darryl. I do think it much better to remover the flappers though, I can't see ever getting the connection point masked off, and it really isn't a big deal, unless you knock the removed flappers in a pile.