What exactly is cross-controlling?
cross controlling is how you enter un-coordinated flight. it's like doing a forward slip.
imagine you're on final aproach to the runway......but there's a 10kt wind directly from your right. if you fly with your nose pointed the way you're flying, the wind'll blow you off to the left. so to counter this, you dip your right wing into the wind. but now, your airplane wants to point the nose that way, so you use left rudder. now, you're flying with your nose straight, but your right wing dipped into the wind, thus countering its effects.
you could also do the same thing to bleed speed and alt very very quickly on ........you're 2k alt, need to get on the ground fast.........full right rudder, then just enough opposite aielron to counter, and keep you going where you want to go. but this time, your nose will probably be pointed about 10 degrees to the right of your flight path.
i think i've seen guys do that to get shots too......and to force an attacker to overshoot, as when you do this, the whole side of your aircraft becomes an airbrake.
i think i got that out of my head right.