Well, I bought sanding disks and flapper disks at Harbor Freight, on my lunch break, and did a "test" section on the trailer. I don't think it's bad enough for blasting. The crevices are going to be a PIA. All I had on hand was the brown primer....The other two cans are grey. It's also sitting on the axle again with the bolts on the spring hangers hand tight, so I can roll it around the driveway.
I hit it with some krylon rusted metal primer and it looks pretty decent.
While I'm at it I'm modifying the rear mast stand to allow access to the sail tube. I'm going with a wishbone shape.