If the headstock on the lathe is short enough you can support the chamber end of the barrel with either collars fitted to the lathe or a spider. Use a 4 jaw chuck on the muzzle end, since the bore is almost never concentric with the outside. I use gauge pins to indicate the bore, you could use a tenth indicator just inside the muzzle as well just don't scratch the bore. Then turn and thread like normal to fit your brake. Then I set the compound at 11 deg. and cut a normal target crown. Check your indication, you do want it less than a tenth, and make that critical final bevel cut with a razor sharp tool ground just for the occasion so you have a perfectly concentric exit with no burrs whatsoever. That's it - takes me maybe 15 minutes to do but I have all the tools ground and mounted that I need.
If the barrel is too short you have to either pull it off the action, or make a mandrel that slides into the bolt raceway to chuck up on, use the live center in the muzzle, (or use a button you have made to fit) indicate the chamber end of the barrel, thread the muzzle, then set up the steady rest and figure out how not to mark the finish so you can cut a fresh crown and polish everything out by hand. You don't get as nice a crown this way but if you are careful you can do a good job.
For installing a single brake on your own gun it is likely not cost effective to do unless you are just bored and want to do everything yourself. You will also have to make the brake and fit it (match taper, clock to TDC if using an indexed brake, blue it or otherwise finish it to match the rifle, etc.)
I routinely repair rifles that people have tried to use dies to thread the muzzle on. Usually this requires a cut and crown, frequently having to drill and tap holes to move the front sight back, etc. It ends up costing them many times what it would have been if they had just brought the rifle in for a brake installation in the first place.
