Due to the crappy wind of late I have found myself trying to pump onto the plane quite often. I know I don't have a good technique yet - my results are pretty mixed.
What are the key points? Is pushing the board away part of it? Is it mostly backhand or some sort of scoop? I find sometimes I can get the board planing them I try and get hooked/strapped in and I've lost it 
Thanks in advance!
out the harnes.
bear off on to a broad reach.
pump equally with front and back,slight bend of ze knees, USE the whole body to pump - not just the arms.
try and get your weight off the board and over the water helps.
use a bit of swell to make life easier.
keep going, keep going, keep going, keep going, keep going,...nearly there, keep going, keep going YES ur on the plane...3 seconds later wind drops, u stall . start again 
once ur on plane maintain speed thru lulls with small backhand pumps.
maybe just put front foot in strap, untill u feel u r going fast enough to put the rear foot in
My own corrupted, misguided kooky method primarily involves mainly bouncing the board by pumping more with my legs.
I found I had to do it this way with some of my short boards as just pumping the sail wasn't enough to get it going. Possibly helps break the board away from the water.
Really bear away a lot, start with a couple of big, exaggerated pumps and try to make them smaller and faster as the board (hopeully) accelerates. Try super hard to keep your weight on the mastfoot and keep the board flat, flat, flat.
You can try a kind of scooping motion with the sail combined with almost jumping up and down like on a trampoline, but with a forward/sideways motion to try and unstick the board.
The downside is that you still need wind to plane.
You can lose a lot of ground downwind pumping like this and still not get planing, so pay attention to where you are!!!
The key, if you have enough breeze that is, once you get to the point that the board feels like it should be planning, sort of pump down with your feet, you sort of do a little jump off the water then hey presto you start to fully plane, what the little pump on the board does is pop you over the bow wake your pushing through the water, and pops you on top of it. i also sort of have the sail pulling me foward almost throwing me over the front, keeping my arms straight and my legs, arched back to weight up the harness, this works great, i usually use the same size sails as the guys 15kgs lighter than me, on a board for my weight and plain about the same time..
I like the sail pump foot pump combo while sacrificing a bit of upwind to catch any runs, but have found that using a wave sail like an older Ezzy I need to give one big pump whereas with an onshore sail a few smaller pumps works better for me. I think the longer boom might allow this.
