I tried a few methods and the most successful was to mount the Dremel pointing straight down at the ground and have the work area VERY well lit. It's very fast, and the learning curve is steep, but it's way better than starting the slot with a Kemper saw imo. There will still be plenty of needle file/SP work to make it pretty but this will definitely save time.
ETA: sorry the photo angles are weird. I was holding my phone between my knees lol.