Not sure whether you are working on a blank, a pre-inlet stock or an existing rifle. Similar to Mark, when I put a swamped barrel in a blank, I just rough out a straight channel using a gouge so the side flats come as close to the stock as possible. Then, set the barrel in the channel and using a sharp knife, mark the barrel outline on the wood. Using a sharp chisel, cut close to that line. Some people like to cut down vertically, I prefer cutting along the barrel length, both work if you are careful, just watch the direction of the grain closely. A chisel is a chisel, there is no special technique involved. no reason not to push it forward.
Using either inletting black or smoke from a small jar with mineral spirits with a hole in the lid holding a burning piece of rag, or a candle as you prefer, lay the barrel on the channel and lightly tap. Then it is just a matter making slight shaving cuts to final fit by cutting away the marks. Use caution on the side flats, once the barrel drops down into the channel, you don't want to keep removing the marks or you will end up with gaps. You will only be working on the bottom flats then.
I never understood why people think that inletting a barrel is so difficult. It really doesn't take very long, no special tools are required and only takes about 4-5 hours tops to get a perfect inlet with no gaps. The key is visualizing the octagon shape, keeping the tools razor sharp, watching grain direction and taking very small shavings. If you cut deep with your chisel instead of shaving, you will eventually tear out some wood, especially if it is very curly. I have never used sandpaper in a barrel channel, sandpaper and sharp chisels don't get along. Scrapers are much better. They are easy to make.
Just do it and you will be fine. It isn't rocket science. Good luck!
