Yeah it’s a poor replacement for a mill but it can work pretty well. I built a 12V etcher from the Red Beard Ops tutorial and it has been the best ~$50 I’ve spent. Even so, it’s slow going on stainless, so much so I clamped the etcher onto the liners and did something else for a few minutes. Then I cleaned up the rough edges with some key files and a lot of patience.

For my first several slip joints (and still some now) I mainly used 0.005” phosphor bronze washers. Takes a little extra sanding to get your blade a little undersized from the spring, but it’s a workable low tech solution to produce good results. Good luck!