Been dealing with this particular joy since 1979, so I may have a little insight....
My difference is, despite sometimes encountering salt water, I don't think I have ever had an adjuster rust up.
I do have an advantage though, since all my trucks have been Fords, they all have adjustment holes in the backing plate.
My adjustment problems are always due to mud. It gets in the little threads and locks the adjusters solid.
As my brake pedal gets lower and lower in the course of a month or so, I finally get out and get under with a brake spoon.
If the adjuster is too solid, I spray some water in the hole or find a small creek to park in for a few minutes.
BTW, leaving the adjusting hole covers off seems to help. Lets the water drain out faster.
I once put in to solve the problem once and for all. I put the adjuster body in a lathe, turned a groove in it. Found some soft rubber tubing that would go over the body and loosely clamped it over an O ring in that groove.
Lubed the O ring so that it would turn easily.
Bunched the tubing up so that it could expand and glued it to the threads against the star wheel.
Light grease inside the tubing.
It actually seemed to work for a while, but eventually the tubing failed to turn, wound up around the threads and tore.
Since my main problem is it not adjusting, I once bent the adjusting lever so that it got a better bite on the star wheel.
All that did was chew the teeth off that section of the wheel. When that mud hardens, its strong.
Nowadays, I use genuine Never-seez. Take the adjuster apart, coat the threads with it and run them all the way in and out a few times.
Then some good synthetic grease under the cap on the end so that it turns freely.
"Wet" grease on the threads just collects dirt.
My best advice you, is cut an adjusting hole in the backing plate. Do the lubing I do.
Make sure to use the never-seez around the center hole on the drum.
If you do go in salt water, flush it with fresh as soon as you can.
As for getting the drums off, with the adjusting hole, you should be able to back the adjusters off.
You may have to use a small long screwdriver or some other tool to hold the adjusting arm back.
Try it with the drum off first to see what you have to do.
Also, although I never did it, I always considered drilling a small hole above the adjusting hole to insert the screwdriver into to push the plate back.
I seldom have to back the adjuster off.
If all else fails, like he said, cutting the heads off the two small locking pins will let the whole brake shoe assembly come off with the drum.
