Only auto-attacks work for increasing your weapon skills (Shot and Autoshot both work for ranged weapons).
@Galenwaithien (btw could you maybe change your forum name so it is more difficult to spell? It is a little bit simple for my tastes) an Axe might be more useful
As a general disclaimer going afk can be bad for your toon. People could MPK it, or kill the cocoon so it spawns a mob that might trouble you if you are completely not paying attention (at least you won't be increasing your weapon skills).