@koolatron Thanks for having a look :).
I am using a Magnum Sharpie (very wide tip) as a etch resist, but not as a solder resist – tested that and the solder will burn through it. I only got Dykem yesterday, it is weirdly hard to get in Canada, so I need to test that more. It takes longer to dry, but might work as a resist. I’ve used dry photoresist sheets as a solder resist, but it is a little time consuming, and a little tricky to line up perfectly on both sides. I didn’t find it that much better for soldering tbh, but it did look much nicer – need to experiment more there. I also have been experimenting with 3D printer UV resin. The easiest way there is just add a bit to the board and scrape it into the etched grooves with a plastic – I find a few playing cards taped together work well as the scraper. Then 5 seconds in the UV lamp and it is ready. That resin does seem to make it easier to solder, but you need to be sure no resin stays on the surface. In the end though, I’ve gotten a bit more used to soldering these kinds of boards and now just tin them and don’t use a solder resist. I’d love to find a fast easy way to get that right though. I’m getting a laser printer soon, if the registration is consistent I think blasting away paint or enamel might work well.
I generally try to scratch a bit into the copper, but not into the FR4 board. 0.03 to 0.04 mm seems to work well, enough to widen the track a bit, but still lots of copper left. I’m surprised how well the Nomad goes through a bit of copper, basically at max speed. I’ve also done double contours in FlatCam, that makes soldering much easier, and can clear the copper completely away even (to the point you hardly need to etch). That does make the spacing a bit wider though.
You are right I can drill before etching, that is mostly me being superstitious about the etching removing some copper around the holes. I need to do some comparison test with this, but I’m sure you’re right and the difference will be negligible. The registration is really precise though, the rivet nuts hold the board on their OD, so re-registering to drill is quite precise (assuming I put the board back in the correct way up that is ;).