manawar, *I* wouldn't use MF for washing. I'm a bit of a chicken when it comes to that (both its strength and its weakness). By its very nature it will hang on to dirt, even after rinsing in a wash bucket (it will need a lot of agitation in detergent to release contaminants).
I feel its too risky, especially if you can use a sheepskin wash mitt.
Don't be too concerned about how *course* some sheepskin feels. When wet they will soften and not induce marring. Its what can get trapped *in* the mitt that should be a worry, and sheepskin should buffer the dirt when on the paint, and then release it quickly in water when rinsing in a bucket.