I use compressed air on mine. In a pinch when someone borrowed my pancake compressor I used a gimpy tire compressor from my car (costs like $7.96 @ wm). Or you could go the route my brother went and use an electric snow/leaf blower which apparently made it spotless lickety split
. Previous to that I did the Rice thing and it works ok for the plates but can leave a lot of dust in the rest of the unit. Is really great for cleaning off oil if you use it though. That's just on coronas tho. Not sure about the roller mills although I can't imagine it would pose a problem to clean them with air either. Just make sure to wipe down what you can cleanly get to after the fact if you use air as it can be a bit moist if you don't use a dryer.