I used 32oz in a 5 Gallon Stout secondary and wow it tasted like coffee going into the bottle. It's also Black..not dark not brown BLACK like Crude can't see any light through it.
We'll see how it is next week.
But what we did was 24hrs with enough Coffee grounds to make 8 cups sitting in the 32oz of water in my fridge, with 3oz Jameson and 3oz Bailey's. Came out a light color so I can that mixture through my coffee maker...still kinda light. Added to my secondary started to add the beer from the primary and it got lighter....then turned all black again. I figured that wasn't going to add any real flavor, so it sat for 2 weeks in secondary. When we opened it, wow yeah coffee, but not bitter. Not much from the Whiskey a very little of the Irish Cream.
Anyway figured I'd relate our experience.
Will I try it again Sure, less coffee or just go with the coild brew and not mess with it.
BTW Used Sumatra Coffee so it is a bold flavor to begin with.