After watching this video:
I set out to learn the double haul.
Had a lot of trouble at first, but started to get the hang of it near the end.
1. It helps to have at least 20' of line; otherwise you'll be haul really quickly w/ you left hand
2. Be sure to take the haul w/ the left hand, having enough line to bring the line to "dust the pocket," and enough clearance that you won't be taking line from the reel when hauling
3. It's key to have a tight line right after pulling down on the haul whilst "pushing" the line back to the reel.
4. RELAX the right arm, but keep the same 10 -> 1 o'clock positioning, and don't overpower the rod.
5. Let the haul/left arm/hand do all the work.