I can't say as to I've tried it much on electronics, but with dunked electrical
items, I do the following to bring'em back to life.
First, a good rinsing with fresh water. I suppose distilled would be the best if you've got it.
Then I wash out everything with rubbing alcohol, to flush out the water. A pint or two at least, depends on the size (and value) of the item.
After which I set it somewhere, like say on some newspaper on top of an angled board/resting at an angle(s) where it'll drain best... with a fan, or space heater set on low, pointed at it.
In theory, at least, the alcohol will flush out the fresh water. Which itself, has gotten rid of the salt
. And it being "clean" alcohol, when it evaporates there's not much residue. As denoted when you use it on your skin.
'course some folks swear by baking dunked items, or putting them in bags/bowls of rice. Just other ways of getting out the moisture I suppose. And one, or all of these might even work on some electrical panels in a pinch. Assuming that your wiring's properly labeled, & won't get to arcing & sparking off of itself if you have it hanging loose, sans panel.
Disconnect main power at the battery
temporarily perhaps, while the panel's undergoing Frankensteinish experiments to revive it.