First thing to do was grab the can of WD-40, a BUNCH of paper towels, rubbing alcohol, paste wax, and some 320 grit sandpaper.
Next place the jointer, unplugged, on the bench. This WILL make a mess, so I recommend placing newspaper down on your bench if you care about the finish of the bench...
Next swing the cutter head guard out of the way, in all processes be VERY careful of the cutter head, those blades are supposed to be sharp and can cause serious harm! with the guard swung away thoroughly spray down the tables.
Sunhill 6" bench top jointer with rust, and WD-40 on the tables.
Let the WD-40 soak in and do its thing for 15 minutes or so. It seems the longer the better. In my case I washed the car, then I came back into the shop to work on the jointer...
Once the stand time is done, get busy scrubbing with your fine grit sandpaper. Just use small circular motions. The rust will come off VERY quickly, at least the brown red stuff. The black discoloration takes more work. The WD-40 will turn into a sloppy rust colored mess VERY quickly. Work the entire surface until all the brown rust is off. Wipe the surface and any surfaces the slop got on off. In my case the housing had some WD40 rust slop on it I had to clean up...
Spray down the tables again, and using a clean piece of sandpaper, repeat gently swirling the rust away, including the black stains. And again wipe all surfaces as free as you can of the WD-40.
Using a clean paper towel, and rubbing alcohol, clean the WD40 thoroughly off of all surfaces. Still being careful of the cutter head blades!
Finally apply paste wax to the cast iron surfaces by dabbing a bit on a paper towel, applying in a circular motion over the entire surface until it gets a haze, then wipe the excess off with a clean paper towel. Your jointer should be ready to plug in and use now!
The process of rust removal should be very similar for any other cast iron table surfaces on your woodworking equipment. Keeping your equipment maintained makes it easier to use, more effective, durable and safer for you and others. A worthwhile investment in time and energy!