Hip/shoulder seperation drills and starting the lower half

im a 17 year old high school pitcher and i throw between 75-78 consistently but ive topped at 83. i know i dont you use my lower half nearly enough so im looking for drills that will help me with my hip/shoulder seperation and drills that will help me start my lower half first and get it more engaged. any help is appreciated. Thanks!

http://www.letstalkpitching.com/phpBB2/viewtopic.php?t=17067

The Hershiser drill will let you practice engaging the lower half. In particular, it will let you put focus on the timing of when you start moving your hips (sideways) towards home plate.

When doing the Hersheiser drill, I like to over exaggerate staying closed off with the stride foot. I found that this can help with the feeling of staying closed longer during your stride when you move to the field.