What are you specifically having trouble with? Walls? Sweepers? Any specific type?
Gyrados is pretty frail and one good electric move or rock move can decimate it. Maybe use either a Focus Sash or.....have it hold King's Rock or Razor Claw/Fang (whichever gives the flinching effect) Waterfall and Ice Fang both have a 30% chance of flinching and kings rock makes it I think 50% which can save your hide. These are only suggestions.
For Hydregion....teach it Earth Power over Surf. EP covers as much as water does and then some even at slightly less power.
You see I am simply one hell of a Nobody