Wanted to give an update to this in case it’s helpful to others (and because Charlie and Travis’ thoughts above were really helpful to me). I filled the channels with brass powder and used some thin Starbond CA glue to slowly saturate each feature. This ended up taking forever (3-4 hrs) and making a mess but gave a nice, shiny metal finish when sanded down.
The main problem I had was that sanding down the surface continued to reveal powder voids where the CA glue didn’t penetrate far enough. I probably did 6-8 touch up passes of applying more powder and CA glue before calling it a day and just trying to keep sanding to a minimum and handle the piece gently to avoid more break throughs. At the end of the day, this will hang on a wall/shelf so it’s not gonna see a ton of wear.
Moving up in sandpaper grits made superfine metal dust that stuck in the pores of the wood and muddied the curly maple a bit. Nothing huge but definitely room for improvement on getting a nice finish on both inlay and base wood.
Overall I’m really happy with this piece and think it’ll make a nice gift. I love the brass luster and how it fades in and out of the curly maple depending on the light.
Two ideas for next time: 1) finding an even thinner CA glue and trying this powder saturation method again, 2) making a superthick sludge of brass powder and epoxy and see how that cures and what kind of finish I can get.