Hi Wet Willy,
What an interesting set of responses! I've only been windsurfing for about 7 months, however my catapults decreased dramatically when I realised that I was standing too far forwards. Specifically, moving the back foot back as far as you can really reduces catapults.
I think my last catapult was about 4 or 5 sessions ago, and I get into the harness as soon as I'm standing up, so I'm in the harness about 95% of the time. I've gone from say 20 catapults per session to about 0.2, all through moving my back foot back and having a wide stance.
When a gust hits, I'll sheet out slightly, get my weight back, and then sheet back in to take advantage of the gust. Perhaps this is the wrong technique, I'm certainly not the first person onto the plane, but it does stop catapults. Getting the back foot as far back as you can REALLY HELPS!! Also keeping the harness line attachment points close to each other (like 2 cm) means that the harness lines don't rub on the harness hook, meaning less friction, meaning you can sheet in and out quicker.
Now as for pumping, I haven't figured out how to pump to make myself go quicker, what normally happens is that I pump away and as soon as I stop pumping I grind literally to a halt... then it takes a bit of time for the wind to get me going again. From what I can gather it depends on the type of board and sail you have as to what type of pump to use (small twitches of the back hand or massive violent unhooked reefs of the sail).
I guess you have to find out what works for you. Right now I'm staying in the harness all the time unless I feel like I'm about to start planing and then I'll try unhooking and pumping to get onto the plane, but it never quite works the way I think it should