You're on the right track with Corrosion X. I'm neck deep in the forums on this subject right now and here's what I've learned:
The simplest path forward for small areas:
1. Gently remove the bubbled clear coat with a plastic card (think credit card like) or use another small scraping tool.
2. Dab or spray with Corrosion X. Wipe excess dry.
3. Seal the area with clearcoat (you can use a pen from an auto store or plain clear nail polish).
It won't look great, but it will stop the progress. It goes without saying that you should wash and wax the trailer after the fact. Continue treating small spots as they appear.
For larger areas you can replace step 1 with some gentle wet sanding with 1500
and 2000 grit to clear the corrosion from the skin. Some folks have had luck getting a decent paint match before clear coating (either way it's not going to be pretty).
For grab handles, bumper, and cast pieces, you can sand those free of the corrosion, polish and clearcoat (ideally a spray). This is far more involved, but the outcomes are better in terms of appearances.
Note: There are probably way more areas than you realize. Really give the entire trailer a close look especially at the seams, rivets, and clearance/marker lights. It's also not a bad idea to use that clearcoat pen on all the exposed seams.
Sorry you're going through this, too. It can be stopped, just not fixed.