Air Force drug testing: Urine, Blood, or Hair follicle?

My friend is thinking about joing the U.S Air Force. He last smoked about 2 months ago and hasn't touched it since. He went to a recruiter a few days ago and they asked if he did it more than 15 times. He said no (that was a lie.) Is there anyway they can check to see how many times, and what kind of test is it they give you?