A very fun way of destroying signs:

1.When yoshi get a power flower,burn the sign.
2.Press B then R at the top of the sign with any character.2x for Mario,Luigi and Yoshi,
1x for Wario.
3.Press A at the back of the sign then press A again to throw.Only Wario can do this.
4.Press A at the back of the sign then press B then R to destroy.Only Wario can do this.