I've never found any of the methods offered on here to work to a satisfactory level. Of course this is based on my experience. I've used all of the methods mentioned on this site. No method ever proved viable to adhere dope to. While the dope went on, in short order I could see discoloration within the oil soaked areas through the dope and then failure. K2r is a great product for making you cough your b-lls off even using a mask. It's horrible stuff when initially sprayed on. Yes, you can see when the powder forms that oil is absorbed into it. It takes so much of this stuff not too mention countless hours of trying to iron and soak this stuff out and in the end the balsa doesn't even sand correctly. You never rid the wood of the oil.
I then tried the acetone and lacquer thinner wash using Klean Strip products which caused the ply to delaminate. Not the plywood itself but the bond to the balsa. I then heated Systems 3 T-88 and let that run into the separation which did glue the ply back onto the wood. I chose T-88 due to it's ability to glue exotic oily hardwoods. However, in the end, the time, the money spent for all of the product I could've built another plane .
I know the feeling and it's difficult to part with something you really enjoy. In truth, you really have to be committed to a project due to this problem because it's not a easy fix and in the end, the bad outweighs the good and you now have a plane still falling apart.