Yes, there are 3 holes that open when you turn a plate that is riveted to the kettle. Would be a simple process to use that plate, unless it's aluminum, for the filler to close the vents. Sounds like a good idea.
I can still remember watching him on PBS with my dad when I was a kid, back before we had cable where we lived. My dad and I used to both get a kick out of him. I remember watching the "Frugal Chef" as well.
The electrical rust remover usually involves a plastic tank not a metal one. I've made them of all sizes the biggest being a plastic trash barrel when I was cleaning up an axle, wheels and various other parts from a boat trailer I used to make a garden tractor trailer. Basically I dissolved Arm & Hammer wash soda in water to make an electrolyte, used a old battery clamp with a solid copper wire attached to clamp the piece I was removing rust from then clamped the negative from a battery charger to the wire that was out of the water
Then used a old copper bar about 3 feet long for an electrode (I bent it to get it all in the water; rebar, metal mesh, anything steel/copper, but not stainless, can be used) with another copper wire attached to it then the positive clamp was attached to it (did not want to put my charger clamps in the water) made sure the electrode and the piece the rust was being removed from were not touching then switched on the charger and waited until all the rust was on the copper electrode. You usually want the electrode closest to the rustiest part. Depending on how rusty it is you might need to change the water and clean the electrode occasionally.
Wash the item down afterwards, conversion coat it, epoxy primer then top coat. This will remove even the thickest rust but of course if you knock off the thick stuff it does go quicker.
For a parts washer we've always have just welded up a box (with a higher shelf area to work on and a large deep area for soaking and to allow the grease to settle to the bottom and a can to dip solvent with) with a lid and legs and a drain (this is for our home shop; OSHA would have a fit if they saw it in a commercial shop). But to tell you the truth a $100(less a 20% off coupon for $80) Harbor Freight one would work just as well; they really don't appear to be much different than $200+ parts stores ones just don't expect commercial duty. Of course my Father's diesel powered service truck with a valve and line on the fuel line to fill a bucket with fuel always worked very well in the field ;-)! A plastic tote with a lid is also a good, quick and easy parts washer as well.