The best way is with two person both using fire bombs changing between 2 spots. Here is the explanation:
We have spots A and B, and 2 charactes (1 & 2)
Person #1 put Fire Bomb in spot A, and go to spot B where is a fire bomb of person #2. Both of you Kill the Gryphons making sure that the fire bomb of your friend hit the gryphon. When fire bombs ends, then both of you Put a fire bomb on your current spot and switch.
Here are the spots.
In killmaresh mountain here: