Specifically, I'm using Banshee on linux for my music player, and my mp3 player is a Sansa Clip+, but I wanted to keep the question general for all MSC devices.
I added a .is_audio_player file to both the Clip+ and its card, so now they both show up in Banshee. But I want to be able to just sync my library with it, instead of trying to figure out how much to drag to each half. Is there a way to do this, or am I out of luck?
Edit: I don't plan on switching cards in and out. I'm using the MicroSD card solely to increase the capacity of my Clip+, not because it is removable.