You can get MooMoo Milk in G/S/C. And yes, I've used the Exp Share many times when I had new Pokemon I wanted to add to my team. The one who used it the most was my SS Dewgong, who hatched as a level 1 Seel when everyone else was past level 30.
As for Hyper/Max potions, I've only ever used them on Vaporeon, who was not as much an HP continent as Blissey, but maybe an HP island. And Super Potion can be good for light healing, but Fresh Water is cheaper and heals just as much, so I only use the Super Potions if I've found them, I don't buy them.