I have been thinking about doing everything separate then putting it together and see how it affects headspace. Every rifle I have Cerakoted so far has been a completed rifle except for bedding when I coated it. You have to get the lube out of the threads or it will ruin your Cerakote. I put a little break free CLP on the threads and the face then blow it off with compressed air so there's just a light residue of oil and then tighten the barreled action and then start soaking in mineral spirits then acetone then gas the assembly out at 3++° for 1 hour and repeat acetone gas out till nothing seeps through. It's a pita sometimes but necessary for a good finish. So I'm thinking about breaking one of mine down and doing it all separate and see how it goes for me.
The way it looks to me if you did everything separate on a Remington 700 and increased each surface (action face, each side of recoil lug, face of thread tenon, bolt face and receiver lugs & bolt lugs) by .001 you would increase your headspace by .001 then when the coating wears off of the bolt lugs and action lugs you would be another .002 excess on headspace. Then take into account those machinist's that try have a perfect zero clearance fit on barrel threads another .001 around the threads and the barrel is now to tight by .002.
There's a individual employed as a gunsmith somewhere in the U.S. that I told I did a little Cerakote and he claimed his work was so critically perfect that his barrel threads couldnt withstand any buildup and still fit not even another tenth of a thousandth of and inch of Cerakote. I'm not a commercial Cerakote applicater I do what works for me, I have found by blasting with finer grade of aluminum oxide and spaying thinner coats of Cerakote I can cut down on the buildup to less than .001 and still have a durable finish . I will find out some time soon how well it works out for me when I start with a Cerakoted action then fit a barrel and then plug the chamber and muzzle and Cerakote it threads and all. I like a little clearance in my threads so I'm sure it'll fit when I'm done.