probably lots of ways to do this, but I've just leveled 5 lvl 20-22 pets up to 25 in the course of an hour with the Darkmoon Faire Trainer. here's my lineup:
Lil Deathwing - Tail Sweep / Roll / Elementium Bolt
Fluxfire Feline - Pounce / Windup / Supercharge
??? - Profit!
start with Deathwing vs. Eye.
1) Elementium Bolt, Roll, Tail Sweep and the Eye is less than 200 HP and stunned. He swaps in Tonk. Tail Sweep until deathwing dies.
2) swap in leveling pet, attack 1-3 times to finish tonk. Hopefully still having at least 1/3 of your HP left
3) Eye comes back, takes one hit and dies.
4) perform 1 action with the leveling pet against Monkey, which will eat the Stun.
5) swap to Fluxfire, and do the typicall Windup, Supercharge, Windup
If you are really unlucky with misses/dodges, you may have to forfeit and restart. biggest challenge is that I'm winning faster than the 8 min cooldown on Revive Battle Pets, but fortunately I have tons of Bandages....