Had no probs with F lounge in LAX having qualified in the middle of a DONE4 - they just gave me the swipe card when they looked at the ticket
BA lounge in JFK was more of a problem. She said Business lounge to the right - I said just qual'd Emerald, its on the ticket and walked left... Didn't get pulled up.

(Also I didn't need to remove and reapply my QF number - it propogated automatically to both AA and QF)