Swimming with long fins really helped me get the feel of the two-beat kick.
50m with two fins, 50m with right fin only, 50m left fin only, 50m both fins. Kick gently, arms outstretched in front of you for 10m, then slowly start full stroke swimming. You'll start to really feel the kick originating from the hip.
It's the only thing I'd use fins for, but it really helped me.