Regarding Brock:
If you’re unlucky enough not to receive Mankey (Low Kick), Nidoran (Double Kick) or Caterpie (Confusion), then Pidgey is your next best bet. Why? Because ‘Sand Attack’. Lower each of Brock’s 2 Pokémon’s accuracy to naught with Sand Attack, then menacingly chip away at their health with Normal attacks. Throw a few Growls in from Pikachu if you’re worried about taking damage.