Never cleaned mine yet. 1 month + and still vapin' up the place.
However I have cleaned my 901's and penstyle to sample flavors.
I use an air compressor, but would not recommend that method.
You can easily use to much air pressure and kill your atomizer, and I would feel bad.
Some folks just blow them out, some rinse with water first, then use a hair dryer, oven dry at about 180 F, air/drip dry over night, shake and blow, whatever you like.
I think it's important to get rid of any residual water used asap, but that's just me.