I'm still getting this dialed in on my 18... bringing my crew up to speed AND thinking about myself is tough! Two very different things, really.
I'll reiterate that weight transfer really makes a difference... I go to the back corner for a tack and stay there holding the mainsheet through the eye of the wind, and THEN cross under the boom -- also moving half-diagonally forward but still in arms reach of the tiller bar to keep carving the turn. I'm holding the mainsheet as I go which creates a little slack. As I complete my cross, I'm picking up the tiller extension, pulling in sheet as the boat accelerates, and working forward to mid-tramp to smooth the water flow along the hulls.
Here's a pretty good walk-through with video and commentary:
https://www.youtube.com/watch?v=bMka3IeyNQoRandii