John in NM
When I do it (rarely) I use my dad's old set of Dem-bart cutters. They are basically just handles with tiny sections of a file that can be swapped on the handle. Some are single V and some are 2x or 3x V's at various line per inch spacings. I have a few that have 2x V's but one is smooth and the other cuts, for working in a line without overcutting the line before that is the reference.

There was a company that made power checkering heads in Deming NM, not too far from where I live, but they went out of business maybe 10 years ago. It was undoubtably a sole proprietor who either retired or passed away, as the market is very small these days. They turn up on ebay often enough, but I don't do enough checkered work to justify the cost (usually $1k or so). Checkering by hand is more fun I think, but then I don't have to make $20 an hour doing it - probably $.50/hour the way I do it!

More often I stipple finish textured grips. I make one in particular where that is the traditional look. Its what you see on Anschutz target rifles if the term doesn't bring up a picture for you. I never could find acceptable tooling for that, so I made my own (and the first was a hand tool too )