This is a very handy Baton pass set which has helped me out a lot of times. You can choose from the physical or the special one.
[email protected] berry(special)/Maranga berry(physical)
IVs: As much as you can ;)
EVs: 252 Hp/ 252 Def(special) or Spd(physical)/ 4 Att
Nature: Impish(special) or Careful(physical)
-Bulk Up(physical) or Calm Mind(special)
So here's the logic:
For the physical set you will pass down Att and Def boosts from Bulk Up, an Spd boost from the Maranga berry and Spe boosts from Flame Charge. A careful nature because you don't need Spa but you do need the Spd boost and you should also put 252 Evs on Spd since you can already boost Def with Bulk Up. Roost is there to heal.
For the special set you will pass down Spa and Spd boosts from Calm Mind, a Def boost from the Kee berry and Spe boosts from Flame Charge. An Impish nature because you don't need Spa but you do need the Def boost and you should also put 252 Evs on Def since you can already boost Spd with Calm Mind. Roost is there to heal.
Furthermore, you should put 252 Evs on Hp for maximum endurance and the 4 Att Evs are just there for Flame Charge, although it really doesn't make a big difference.