I haven't played Black white and up,
but my combo back then was
Ninjask:
Agility/Protect
Baton Pass
Double Team
Sword Dance.

Machamp:
Dynamic Punch
Thunder Punch
Poison Jab
Night Slash.

Basically you get Ninjask to Double team once or twice, or if the enemy is some thign that can 1HKO you, just Protect. then buff the poo poo outta it, especially speed. then baton pass to machamp.

then you get a machamp with +4 attack and at least +4-6 speed. pretty much one punch ko everything.