OK, so I think I understand how this works but just want to make sure:

Once per attack roll you can give away any number of dice to a friend or foe sharing your path. They then use that number of dice and their values for either a shock or attack roll. Then Hoss can roll new dice to replace the number of dice he gave away, correct?

So I could in theory roll 4 dice for an attack, roll all 1s then give them all to my target, who would have to use them ( and fail) for his shock roll. Then I essentially re-roll my attack roll using the new dice values. Do I have this right? This is a pretty wicked power then.

I think that´s the way it works.

You got it right! There's only one small problem about it: Hoss will often attack a characters that doesn't share a path with him so he can't give his rolls to his target. If his enemies enter his path to bring him down, though, he can give them his bad rolls just as you described.