Dean was actually fully versed in the weapons he used when he was cursed at 14. He’s trained to use a shotgun since he was very young, with the help of Bobby and his father, and he’s kept a knife by his side the entire time, whether it was his silver knife or a regular hunting knife.
Sam could offer, but chances are that they’re pretty even. Dean would be tempted to challenge him to see who’s moves are better, though that’s a difficult contest when Dean could stand on Sam’s knife!
Jacob is the eternal little brother of these two, they’ll both be willing to give him some help perfecting his moves.