How about a round wire wheel the same diameter as the curl on the bed and a long extension on a drill motor. Or get some smaller wire brushes and fashion some extensions for them and do it by hand. I've done a lot of improvising on stuff like this.
Clean it as best you can, then pour some rust stabilizer/neutralizer down in there and call it good.
Of course, the electrolysis would be better, but it would take a little time to rig it up, and I'm sure it would be fine.
