A coffee grinder isn't that great for milling grains for brewing. You don't want course flour. You just want to crack the grains open,which are smaller than a penny when whole. I used a mini food processor till I got my Barley Crusher grain mill,comlete with 7lb hopper,wood base,& crank handle for $130 from either NB or Midwest.
The mini food processor worked ok with about 1/2C grain pulsed 2-3 times for about 2-3 seconds per pulse. It worked ok for partial mash biab,but too much floury stuff that can get through the paint strainer bag. This due to the blades used in food processors and many coffee grinders.
The barley crusher grain mill has been a great product for me. The price for it being complete & ready to use is a real bargain. The better quality Monster Mills cost a couple of times as much,as you only get the rollers in the framewirk for some $180. you have to buy the base & hopper seperately,driving up the cost. And the Barley Crusher mill has notches on the crush rollers' adjusters for the factory setting of .039",which works really well for me. Way less floury stuff,& very evenly cracked open grain kernals. My OG's actually went up after using this grain mill. Def worth the cost. It's base is made to fit on top of a 5 gallon bucket,like the ones at Home Depot or Lowe's. This way,the poofy stuff is well contained.