The Annoyed Man asked: "What's involved?"
The simple answer is: lots of elbow grease!
Essentially the blueing process simply adds a special oxide layer to the steel gun parts that makes them look blue; nothing more, nothing less. If you don't remove all the oil and grease then the water based solution won't work on that part of the steel that has an oily film and it won't look blue. So it must be cleaned to the point that there is absolutely no oil anywhere. Given that, the steel will when it comes out of the blueing process look just like it did when it went in except it will be blue. If it was scruffy and rust pitted going in then that will not change.
If you want a matt finished parkerized military pistol to look like a gleaming commercial Colt just out of the box then you have a load of metal work to do. This work can be done by taking wet/dry abrasive (sand) paper wrapping it around a wood block and carefully grinding away all the parkerizing and polishing the metal with progressively finer grades of paper until it has a mirror finish before blueing it. This will produce a twin of the $300.00 Colt finish; one that can be called "factory original". All the edges will be sharp, the proof marks will be sharp and clear and the rust pits and any roughness to the surfaces will be removed. The flat surfaces will be flat and the rounded areas will have the correct radius.
The quick and dirty way is to get a bench grinder with a wire brush on one end and a cloth polishing wheel on the other and get after the gun parts with vigor and determination. What you'll end up with is a gun that is gleaming blue but all the edges will be rounded off, the proof marks will be smeared across the metal as will all the rust pits and tooling marks on every surface. This kind of work is what comes out of the average gunsmith's shop for $150 or so. From a distance it looks ok but up close it will look like a half eaten all-day sucker. No mistaking that for "factory original"
"With atomic weapons, as in many other things, knowing what to do isn't nearly so important as knowing what NOT to do." -- J. Robert Oppenheimer, 1946
Wisdom comes from reading the instructions. Experience comes from not reading them!
Use the other $250 for ammo and head for the range. 
This is true for any type of surface finish. I haven't seen any new model Colts, but I wonder if they can even duplicate their Royal Blue finish of yesteryear. With more and more EPA restrictions on chemical useage and disposal I wonder if Colt can even use the same composition baths that they did 30-40 years ago.
