Allow me to share my favorite overspeed eccentric drill - credit to Brett Jones, Master RKC, for introducing me to this approach.
Because it's easier to generate an overspeed backswing with two hands than with one, switch often between two- and one-handed swings. If you're anything like me, you'll find you simply cannot throw the bell back as fast with one hand as with two - but it's worth trying.
I usually use a simple format: 2 reps two-handed, 2 reps left, 2 reps two-handed, 2 reps right, and just keep going that way. Sometimes I'll do singles, sometimes 3 reps at a time. The point is to switch often and try to make the speed, explosiveness, and connectedness of your one-handed swings match that of your two-handed swings. It's a great way of using something you can already do to teach yourself how to do something else better.
KBNJ.COM - Steve Freides, RKC Team Leader