Meh.
Should be done on a lathe, but for the most part, it doesn't make a bunch of difference for most brakes or flash hiders, as they are built to have enough clearance around them that the bullet will pass through if they are screwed on sideways, almost.
Use the 'ebay rental plan', as one fella described it. Buy the kit, use it, sell it to someone else that wants to use it. The kit uses a guide rod in the barrel to guide an annular cutter to rough down the barrel, and the same guide rod to keep the die aligned when threading, yes?
If you are wanting to mount up a close tolerance brake, for instance, it would likely matter more. For a basic muzzle brake or flash hider, a careful person should be able to do an adequate job.
Cheers
Trev