Totally agree with Murf. In the beginning I was getting so many mixed results and a lot of long slow paddles. But once you get it all together, it is magic. I am constantly now just watching the winds to go DW foiling again. 100% addictive!
Some very good points made by Brian (aka Jeffs256).
As exciting as it is DW'ing, you have to stay calm and be patient. When it looks like a good bump is lining up, get into surf stance and start gaining speed. 90% of the time I find the bump I thought I wanted to go for turns out to be too fast and too hard to catch, but generally the one directly behind it (which you didn't even know was there) is usually perfect. So use that first bump to get some board speed up, then as you fall off the back and into the pit between the next one, slam the pedal down with some high cadence and coordinated unweighting and paddling. Well timed you should break up onto the foil relatively quickly (I find normally with in 5-6 strokes I am up onto the foil). Once you've broken the board free, it is a decision to either continue pump paddling (if you are lacking in board speed) or to mainly just concentrate on board pumping (if your board speed is actually quite good, but you're just not quite on the bump yet).
Once you are up and gliding, the next key is to try and keep gliding. Staying high, and keeping with your chop just long enough to gain the speed needed to move onto the next bump (which may actually be behind you in many cases). Smooth transferring and taking note of the ocean patterns is key. You can hunt and chase down swells, but you're going to burn a lot of energy. You are better of retreating from swells and keeping your focus on maintaining a good middle board speed.
Here's a quick cut from a downwinder I did this week. This is the very beginning as I have just paddled out of the wind shadow of the head land. Wind is still gusty and on the lighter side and the bumps are still very small. No swell, this is only wind chop. I miss a few of them, then pic one that feels good and go for it.
Also here is the full vid if anyone is interested. It's bloody long (17+ minutes), but shows most of time up on the foil over a 6.8km downwinder.
Enjoy, and get into it, well worth the learning curve.
Ride safe,
JB