As far as I'm aware, there are only two companies who actually do re-plates, (correct me if i'm wrong anybody) Aptec motorsport and Lancourts.
And its a case of sending them your barrels, (i sent pistons too) they remove the plating and if necessary weld any damage, re-plate, machine and hone to the correct bore size,then chamfer the ports.
All you have to do is admire the work, (quick wash) install back on the engine and go!
You shouldn't have to do any file work yourself. My first (R/H) barrel was spot on (£160!) it did need welding somewhere near the exhaust port. I sent them the second (L/H) barrel and as you can see in my picture, all the ports have sharp edges, no chamfering and in the case of the exhaust port, being made slightly smaller!
I sent the unit back and they addressed all the ports! But after that experience, not sure if I would use them again!
I also suggest uniquely marking your barrels to be sure you are not getting an 'exchange' service on the order - especially if you are going through a third party/tuner and not dealing with the platers directly.