to try to shadow a 777 would be not possible ( read some pages back ). Also military operators do not look at the blips but track symbols. Depending on the radar you would get two very overlapping symbols (one identified, the second not), drawing attention to the situation.
The best chance to fool the military is to fly like everybody else on a published airway. Chances are best you will not be discovered, even if not automatically identified. Unless there is a very good relationship between military radar and ATC, nobody will raise an alarm in the middle of the night.
I'd advise people to disregard the above quoted. It is wholly wrong on several points. I speak from years of experience operating several different types of medium / long range air defence radars,associated command systems and datalinks. The bread & butter is in the "blips" - the track idents come afterwards in many cases. I could go on but that would be a bit naughty.