How did I get the chassis shiny?  Elbow grease, a comfortable chair, Steel wool (non soap), dollar store brass wire brushes, Scotch pads, Clorox Clean up, Brasso, a wire wheel in the cordless drill.  Some times in a tight chassis I use a Dremel Rotary tool and a wire wheel bit.

For the mirror finish I use a cloth buffing wheel on the bench grinder, in a drill or on the Dremel with rouge compounds.  Logically if you can get the chassis or parts to the bench grinder the buffing will go much faster.  But you risk shooting the chassis across the room when it catches the wheel.  

For rust, the wire wheels and plain sand paper with the ubiquitous "Elbow Grease".

Tape up your tube sockets, the holes on the square IF cans and tuning capacitor (close the plates to cut down on the chance that it may get bent) so wire fragments do not short out the electronics.  Or you will have a light show when you plug it in.

The trick is patents and a lot of cleaning supplies.  Wax brass after shining up or it will tarnish again.  A good automotive metal wax or paste wax helps. I also spray the chassis with clear lacquer spray from a can.

Use an old tooth brush and contact cleaner or denatured alcohol on the tuning capacitor (condenser).  BE GENTLE.  Then fold a piece of masking tape so the sticky is out.  Slide it between the tuning condenser plates.  DO NOT BENT the VEINS!!!!  And flush it out with contact cleaner.  I use CRC brand Contact Cleaner found at Home Depot and Lowes. Do not use CRC electric cleaners.  They melt vintage plastic and wire insulation.  I learned the hard way. 

 Get all the old dried grease off of the tuner ball bearings.  Apply a little electronic grease or lube.  I use a small drop of 4 in 1.  Clean off what gets on the tuning capacitor parts or it will affect the operation. Do not over clean the tuning condenser or you may damage it.  A little tarnish will not affect its performance.

 Do not brush and mica that you see under adjustment screws on the tuning capacitor.  Stay away from them.  The mica will easily break and flake causing a short and a dead radio.  You may have to flood them with contact cleaner if oil or dirt gets on the mica while cleaning. 

 You can try and touch up rusted spots (once completely wire brushed) with galvanizing spray, silver paint or your favorite western PA auto body technique.  Again at Home Depot electrical department.

 Just take it easy, protect everything including your lungs with a dust mask (that green metal oxidation/dust is supposed to be nasty) that you do not want small steel wool wires to fall into.  Blow out the chassis and have fun.

 Good Luck.