Use a team of EV'd and IV'd pokemon and sweep up to Palmer's first encounter. (21 in the battle tower) Then, after you get the 20 for beating palmer, start over. (like retire your next battle or something. If you're having trouble due to your team, well, I'd suggest learning a bit more about the strategic aspects of the game. (see strategies & movesets stickies for things like EVs, etc)
If you want to talk particular strategies, I abuse Yawn and crippling moves like Charm or Flash, then have two sweepers to set up and sweep. (borrowed the strategy from a guy named FastHippo if you're curious)