Who trained Usopp?

Who trained Usopp? Heracles is a strange warrior that used to reside in the Greenstone forest in the Boin Archipelago. He trained Usopp in the use of Pop Greens for two years.

Heracles is a strange warrior that used to reside in the Greenstone forest in the Boin Archipelago. He trained Usopp in the use of Pop Greens for two years.