There has been discussion about the use of citric acid to remove rust. .I might give that a try first. I don't know if anyone has ever tried it for this application yet. Stuck clutches are common to 2's and 4's both. .sometimes the diesel soak works, sometimes it doesn't. It didn't with my 4 so I tore it apart to remedy the problem and found the plates glued together with rust.
The problem with the 2 is that the finals have to be pulled, after removing the track and frames. A pain of a job, plus there's a chance that the brake drum will pull apart when you try to pry the finals off.
Maybe someone else will have another idea or two. .good luck hicrop
My old D8-2U and D4-7U have clutches at least partially stuck nearly every spring. I take off with both steering clutches pulled, and do some heavy braking to get them loose. Forward a few times, and in reverse a few. They have always come loose after a few tries.
Good luck
Gary