How do you beat the elite four of Sinnoh easily

there are two strategies that you might use. the first one is to train :D
the second one would be to use Pokemon with strong attack and special attack and don't forget defence.also for aaron use fire types, for bertha use grass types, for flint use water or ground, for lucian use ghost types but don't use gastly,haunter,and gengar because they are poison types.jpoe this helped!