I just used a damp microfiber cloth on my Carbon Leather trim in my previous E90 and E92 M3's. The only part that ever really needed a "
wipe down" is on the driver's door. Sometimes it would get ashy after my hands rubbed against it a few times while opening the door. Other than that, it doesn't require any real maintenance.
Then again, I keep my cars very well maintained and I almost never open my windows, so I never have any appreciable dust build-up.