Hit them once, you will get use to it...with your 400, you can lean back and just "draft" over the whoops.

 

The best way is hit the first whoop between 80 and 90mph and just clear all of them!

And now for real, like was said earlier practice makes perfect. You gotta have good timing, be in shape and precise throttle control to keep your quad revved for the next one.
The first few times they will be rough but as you go over more and more you will get used to them.