It seems like my modular gets covered in dust easily, so I've two questions you guys surely can help with.

Due to the dust a couple of modules have developed scratchy knobs, usually fully moving the knobs back and forth solves the problem, but lately the scratch seems to persist in one of the knobs and I'm not sure how to fix it. It seems like I need to clean it with "air spray", do I need to fully remove the front panel of the module before blowing the air or is it ok to just remove the plastic knob? Is there any other/better way to get rid of the scratchy knobs?

And then, how do you keep dust away from your modular? some cases have a cover like a suitcase, which I guess helps a lot keeping the modular clean, but other cases don't. Do you cover your modular in some way? or how do you keep your modular dust free? So far I've been cleaning mine with a brush, but some of the dust always seems to find it's way into the knobs and sliders.