What I used to do when I was playing with my friends (in 2v2s) was to rush w/ troopers one of them, while my ally rushed the other one.
Then, we continually pissed each others with small attacks until we get air for even more vicious attacks.
When we got to T4, we just massed units according to our civ (dest. droids, bombers, artillery, troops etc.)
~Dark Cupcake of the Sith