I have this problem too. I do the milking, shaking, and even the paper towel -- which never fails to get weird looks from coworkers and others -- but I still keep leaking for several minutes and I rarely have the patience to dry my dick for 5 minutes until it stops. Jeans are thick enough not to show but I always get a visible wet spot with khakis and cargos.

One thing that helps is this: put your hand in your pocket and hold your dick through the picket liner until it's done leaking. Then it's the pocket liner that gets the stain, not the pants.