Just made a coffee stout with 2 oz of coarse ground coffee in 2 cups of cold water overnight... the coffee flavor is there but kinda weak, would probably up it to 4 oz next time.
EDIT: Forgot to mention that this was done in a french press and it was added at bottling.
On Tap: Bitterly Wheaten Down Pale Wheat Ale, Identity Crisis Coffee Pale Ale
Bottled: Grind the Stump Coffee Stout
On deck: 15 gallons of Bitterly Wheaten Down, Curieux Clone