Q&A for How to Defeat Whitney's Miltank in Pokémon Gold/Silver/Crystal

If all else fails, try to drain her milk tank out of milk drink PP. It only has 10 PP, so once it runs out of PP, she won't be able to use it.

Miltank is bulky enough to take a few good hits from a physical attack, so you're not doing anything wrong. Try inflicting some damage from another Pokemon first before using Rollout.

The in-game trade Machop will always be female, so there's no need to soft reset for it.

Instead of elemental punches, there are the Thunder, Blizzard, Fire Blast and Solar Beam TMs.