I've used cold-brewed, grounds in boil, and crushed beans in secondary- sometimes just one method in each batch, other times 2 or all 3 methods in a batch. I always find cold-brewed added to secondary or at bottling the best method.
Get a French press or nylon straining bag. Take roughly 6-8 oz. water, bring to boil and allow to cool. This will drive off any O2 or chloromines. Add 3-4 oz of Coarsely ground coffee beans to the water and place in the fridge for 24 hrs. The coffee should be like "sludge"-really thick. Add to keg or bottling bucket or secondary. Usually coffee is very up front for the first month, but tends to mellow and meld.
Alcohol may be man's worst enemy, but the bible says love your enemy.