I bought a used jointer some time back that had a lot of staining and such on the in/out-feed tables, as well I have a '48 Unisaw. Over the years I've used Boeshield and this and that special coating. The process I use to clean up and protect the cast iron today is: With my PC random orbit car polisher with a 320 disk I will spray the table with WD-40 and go to town with the polisher. I wipe the residue off and clean it really well, rags/acetone, etc. I will then use Johnson's paste wax on the table. There is no silicone in that wax so it doesn't affect the wood. With all the other crap (good expensive crap) I have used my current method has given me the best results. Years ago I had to put my equipment away and it was going to be stored in my humid basement. I knew it wouldn't do well in that environment. I had some remaining POR15 I had used on a couple cars and I painted the surfaces. It took some work to get it off, but the CI did not deteriorate.