Gripo the bike with your knees as hard as you can and lean back while pinning it. There is not much skill to whoops according to Gary Semics, just need alot of guts. He proved this to me when I (novice) went just as fast as him (pro)through the whoops.
Also, maybe you may want to increase the sag a little and make the rear end a little softer on the comp clicker.
1.) Find a relatively fast trail with braking bumps, rocks and roots leading into the entrance of a corner. Reduce (Turn clicker out) the rebound damping until the rear end begins to hop or feel loose. Finally, increase (Turn clicker in) the rebound damping until the sensation goes away.
2.) Find a log or ledge that tends to bounce the motorcycle after hitting it. If the rear end bounces up uncontrollably, add rebound. (Turn clicker in)
3.) Find some large whoops. The motorcycle should track straight through the whoops with the rear wheel extending to the ground before the next impact. If it does not perform as described, as above, it is packing and the rebound dampening should be reduced! (Turn clicker out) (Please note the guide for sand set-up, as these rules don't apply for sand.)
4.) Find a corner with acceleration bumps, rocks, and roots on the exit. The rear of the motorcycle should follow the ground. If the rear end "breaks up", reduce the rebound. (Turn clicker out) (If this fails soften the compression two clicks.) (Turn clicker out)
I am realizing that having to think about the mechanics of riding is harder then just saying it. Dragging the rear brake keeps the rear wheel from kicking up over bumps or obstacles. It prevents the shock from unloading and keeps the rear wheel planted down.
As far as how I am able to do it, I just apply rear brake. It doesnt require a sensitive touch since the gas is on hard and the bike is moving forward with good momentum. It is hard to apply too much brake if the gas is on hard in the meat of the powerband.
The whoops I am referring to are mild compared to Arenacross or Supercross type whoops. I suppose the size of the bumps will determine if this technique is practical or not. Try it and let me know.
I would caution against the whole rear brake thing.If you are going at any kind of speed the bike is rocking or skipping across the whoops so fast, a little too much brake and the front will drop into the whoops slowing or causing you to fly foward and possibly landing right on your head with the bike right behind you.