Charlie--keeping in mind that i am not exactly delicate with stuff---We have the salt and a fine clay suspended in the water on our marsh--At end of season, they always have a lovely patina, which really needs to be gone--
After taking all of the weights and lines off, i put four or five in the garage sink-my float tank, duck washing station, etc., and give the dekes a dose of warm water, to soak, then sprinkle on some comet, and leave them for a few minutes--then i lightly scour with a scrub brush-you can sponge too, while running fresh water the whole time---They are then shelved to dry and the ones needing rehab are taken to the shop..
I have done this for a long time--problem with leaving that rime is that next year, it will just get worse.
You CAN always repaint them after four or five years--that will likely have to be done anyway.
Have had stuff come back this year after over 15 years of hard gunning--paint was still fresh, although there were abrasions, contusions, pellet holes, etc. Oldest that came back for rehab were made around 1985.
Whatever you do, get that crap off the surface!!
The freshwater guys just don't have the same problems as those of us who gun coasts.