When is the ideal time to add ground coffee to my Porter? Primary or secondary? How much coffee should I add to a 5 gallon batch?
Here are some related threads. http://www.homebrewtalk.com/f13/coffee-addition-88854/A home brewing beer and wine making civilized discussion community. Also with beer/wine/mead/cider discussion, beer reviews, pub talk, and general chit-chat. - Search Results for adding coffee to beer
I would recommend adding cold brewed coffee. I added fresh brewed coffee to a stout and it was awful, I ended up dumping it because the coffee was overpowering.
You could probably look through the recipe database and see how much coffee was used for different brews.