Originally Posted by Fat TM13IceBeam
Gastly's pretty simple. Grind to L16, switch in on Miltank, Curse, do whatever it want. You can add on with other things like Poisonpowder from Bayleef.
That's right, I forgot that you can switch out after applying a Curse. There's also the problem of getting said Gastly to that level in the first place with your primary attack being the pathetic Lick. Still seems easier to spam Mud Slap or something...