I finally got around to printing proper keycaps, painting the labels with acrylic paint and sanding them down. I am satisfied with the result, but there is still much room for improvement.

I sanded the caps down to 320 grit sandpaper, especially on the black keys you see, that this is not enough (see the (unsanded) black key left to the ALT key for comparison), but it already has quite a nice feel to it.

I did not print all keys yet, as I am still tweaking the keymap in some places.

The acrylic paint worked okay, although not as good as I had hoped. There are PLA particles from the sanding stuck in the paint and when drying, it contracted, so I had to paint over it multiple times and even the the results were suboptimal. Perhaps next time (if/when there is a next time, I got plenty other projects in the pipeline), I will try colored epoxy - but maybe I will go the whole step to make moulds for the caps.