Innovation comes in all shapes and forms; I take a Dremmel stone circular and drilled a slighter larger diameter pin hole in the face of the circular stone bitt. Lock dremmel in a vice run on medium speed, slowly press the pin into the hole in the stone to gain a rounded edge.I will never forget the first time I mounted sling swivels on my Old Brown Bess Carbine back in the mid 70's. I didn't know what I was doing, had no one to mentor me and even though I had a copy of one of Bailey's first works, it did not explain about needing a heavy barrel lug for the front sling swivel. I had to get the barrel off to measure the diameter so I could spot where to drill the hole for the sling swivel screw.
The curvature on the barrel pins was rather extreme and even though I had a nice selection of short starter pin punches, I just could not get enough "purchase" on the pins to move them. Took some time thinking, but at last I came up with using a tiny dental burr to grind into one side of the pins and have a flat enough area the starter punches would work to get them moving. Driving them the rest of the way out was easy. I filed the ends of the pins flat/perpendicular to the length so I would never have to do the dental burr thing again and just rounded the edges slightly so if I ever had to take the barrel out again, I wouldn't have to worry about sharp edges gouging the holes in the wood larger. I centered the shorter pins in their holes and filled in the small holes left on both sides of the stock with beeswax. Many years later, I saw an original that was done the same way - as far as traces of wax left in the holes to fill them up.
For actually drilling pin holes, I measure with a 90 degree ruler, mark locations on stock, then measure and mark the tape. I start/probe with a very small diameter Drill bitt, if my hit is off the mark I adjust, but its usually not too far off the initial probe then I clear with regular bit and tap the lug. I don’t drill straight through though, I mark both sides and drill on both sides to meet in the center. I use a handrill too, not a drill press. I have a pretty hand jig that works very well for side lock bolts and tang bolts too but not so well for pins.
The Sling swivel I’ve done a few times most important is the measurement from the thimble on the short land. I’ve seen a lot of reinactor guns where the swivel is too far away from the rod pipes and ends up obstructing the loading rod channel.
Wax is pretty essential on a Brown Bess, it maintains the pin mortises and is also great for the barrel channel, creates friction for a tighter fit too.
One innovation thing I do is deviate from on the originals is the nose cap, I secure mine with a small brass screw that threads into a semi circular underlug brazed beneath the end of the muzzle and counter sunk into the nose cap wood.