There isn’t really a good way with the project in its current state. I did have something better set up for the transition to jessie (!) but I’ve not worked on any of that for a long, long time. No idea what state that’s in.
The best current setup depends on exactly what you are working on but I would not recommend rebuilding the image during your development, it’s very slow and usually unnecessary. There are no good emulation options but mounting your development files in a musicbox chroot/container is an option. There is a chroot based script already in the repo. If you are working on something startup or hardware specific then there’s no substitute for running on an actual raspberry pi. I sometimes setup sshfs bind mounts from my dev machine if working with a small number of files. Booting from a network image would be a lot better but I never spent any time getting that working. I’m not sure if there will be any Wheezy related issues there. I’m hoping to dust off the project over the holidays, it has been sadly neglected.