Gary,in no way am trying to advise you on a finish "schedule".You need to figure out how you want to proceed.There's a dz ways to approach just about any finish,be it gun stocks,automotive,or equipment.
Just some general ramblings from decades of painting equipment.
Most...say 90% of old equipment never saw a lick of "primer".It's direct to metal enamel.Hardeners (catalysers) started showing up after WWII.But not everyone used them...
One thing that most manufacturers did and it works today just as well is.....preheat on the part.Metal is cold.Take a pce of CI(cast iron) that's in your 70* shop,and shoot it with a temp gun.Also,notice the difference in temp your shop is with a shot at the floor,then your workbench,now the ceiling.
Heating the part to the upper end of the paints "window" is where it will perform the best.How you achieve that is up to you.But remember the part is going to start cooling as fast as the heat is removed,so be ready.
Attic,your wife's car with the windows rolled up in August,cheap big pancake griddle,small closet with lamps....all will get it done.The paint can be brought up to temp,CAREFULLY in a pot of water on a griddle.
The griddle is really nice.....can be used for bullet moulds and sprues.We take pipe clamp mounted vertical,with another one clamped to it,going horizontally.Using S shaped hooks(fashioned from coat hangars),and suspend the parts a foot or so above the electric griddle,pre and post heat.
Heck,90% of our CI welding is done right ON the griddle.Pre heat part,ramping up over an hr or so to get it up to about 500...weld the pos,then ramp down over a cpl hrs.Start looking for a griddle or two at yard sales,the bigger the better.Get a cpl.
When matching paint,we just look under or at any easy to remove unfaded part...take it to Sherwin Williams or Ben Moore and get them to scan it.We use both of their top of the line enamels with a shot of Isocynate(kill you dead)hardener.No real reason to spend more because the factory sure as heck wasn't using anything better.
Be careful with "fillers" on raw castings.Factory rarely used them.....and when they did it was this black goo that is asphalt based.But way more often than not,they shot extremely heavy coats of warmed up enamel to fill pinholes/flaws.It dries pretty durn quick when hot.
From a restoration standpoint,these are not "perfect" paint jobs from the factory.Orange peel was/is a desirable trait.The pebble is what gives protection from scratches.Just sayin,it's somewhat incorrect to try to get a perfect finish on these pcs.It isn't a car.
Good luck and thanks for sharing pics!
BW