extremely easy method - i am unsure of which act it is, probably 1, but It is done in Silent Woods and can be done shortly after you get there for the first time. it takes zero effort and has zero risk, i did it on hard without even thinking about it.
*** Spoiler - click to reveal ***
you will reunite with your little owl friend and start riding him around. In some of the gusty areas there will be the exploding yellow bubble-like enemies that respawn every 2 seconds or so. one attack with the owls wind attack will blow it into the wall causing it to explode. If you keep the owl off the ground by pressing RT to stay airborne, repeat the attack 5 times before you land and its done.