Wailord needs entry hazards set up on the opponent's side of the field to be effective, as foes can switch around without much trouble otherwise, limiting its PP stalling abilities. Don't be afraid to use Wailord's natural bulk to switch in on threats it can wall, such as Torkoal.
A pony is not a small horse. Horses and ponies are genetically two different species. There are horse-sized ponies, and pony-sized horses, but the genetics are what tells them apart, not the size. A miniature horse, for example, is very small and looks like a pony, but genetically, it is a horse.
Riding Ponies are more like a small horse than a pony, with small heads and ears. They are compact, with sloping shoulders and a narrow front. Their feet are tough and they possess strong limbs.