Nothing works better to clean a grinder than compressed air.
It gets to all those nooks and crannies that a brush can never fully clean.
A brush (foam or bristle) will always compact into seams and joints.
The resultant remains can (over time) become rancid.
As far as storage goes, cupping (and food science) tells me that vacuum sealed in a freezer has no equal.
For small quantities (and short storage periods) air tight, light proof, room temperature storage should be fine.
It should be a no brainer to grind immediately before brewing.
Buy and consume fresh roasted coffee is the best solution.