Its better to use status promblems like stun spore, toxic, and sleep powder then attack whitney's miltank and clefairy with just attacks. You might not have any trouble with clefairy but you most likely will with Miltank. Train a bellsprout into a weepingbell. Give it Cut,vine whip,stun spore,and growth and give it a quick claw and get about 5 super potions, and weepingbell should be on level 23+. This is based on luck but its luck will be higher than other techniques. For the first move on miltank use stun spore and then growth. If you have enough energy for an other hit then use growth a second time. then use a super potion. If Miltank is using rollout watch out because it increases power every turn. The first two Rollouts wont do as much damage, thats two valuabe turns to attack. After two growths keep using vine whip and super potions. You should have a great chance of winning.