I did a few entirely with chisels early on before I figured out just how incredibly inefficient it is. So I went to a combo of chisels and planes (had to find antiques to use or modify) and did that for a number of years before I realized it was STILL taking far too much time. So I bought this little gizmo I saw advertised for a handheld router called a 'micro fence' which is basically a router fence that allows you to make extremely fine adjustments. This worked well and as long as the blank was cut down along the top and sides accurately to the barrel profile (needs to be oversized, obviously) it did speed things up quite a bit. then I just went over to paying the barrel channel/rammer groove guys like Fred Miller to do it for me because for what he charged - and what most of them still charge - it's just crazy to do it yourself. Caveat there, though, I am close enough to a couple to drive and take a bunch at once. Shipping is crazy now so that may affect perceived value vs doing it yourself.
Even if you don't have a router with a micro-adjustable fence, you can still use it to at least rough a lot of the barrel wood out of the way thus saving an awful lot of time. Or you can use dado blades on a table saw, or like Herschel's old videos, a spindle shaper w/ modified bits. Anything to just hog out the majority of the wood, then you can finish up with hand tools.
I've never inlet a lock with a machine tool and don't plan to ever start - too much 'oops' factor for such a small inlet.