You don't need to cheat or anything to do well. All you need is to have a good EV trained team with some kind of protection against luck (Substitute is undeniably the best choice; it protects against critical hits, OHKO moves, and status effects).
Make use of the game's flawed AI. They only switch if all 4 of their moves are not very effective; however, they don't take into account unusable moves. If they only have one usable move which is not very effective, but the Pokémon has an unusable super-effective move, they won't switch and continue dealing very little damage.
The most popular strategy to exploit this is to lead with a Pokémon holding a Choice Scarf and use Trick; that way, you'll attack first, and lock them into a single move. Then, you may want to incapacitate your opponent in some way, such as paralyzing them or decreasing their attacking stats. Switch for a Pokémon which can increase its stats (for example, Curse and Amnesia), put up a Substitute, and laugh at your opponent while you max out your Attack. It's quite tedious, but very effective.