Here the strategy
Pokemon uses curse X times then follows up with gyro ball
Steelix w/ leftovers
Sassy
Gyro ball
Curse
Double edge / Earthquake / Fire Fang
Protect
Pros: Steelix gets a STAB for Gyro ball, lots of resistants, ,It has a little more HP than Torkoal and a lot more DF
Cons: It has greater speed than torkoal, lower SD, has more weakness, highly susectible to low kick and grass knot
Torkoal w/ leftovers
Sassy
Gyro ball
Curse
Amenesia
Protect / Flamethrower
Pros: Less Weaknesses, Amnesia, Slower, white smoke
Cons: less resistance, less HP
If only Registeel could learn gyro ball