While it's burrowed, use any form of explosive to push it out of the sand. Run up to it, click interact and ride it. Anything you break will restore your Control to max, but might not give a lot of torpor. Pure stone gives the least, and the rocks will give more depending on how much stone it would give. Salt, Crystal, and Metal nodes give much more torpor with Crystal and Metal being the highest.

For a strategy, grab onto it, pick up rocks on the way to restore control, and steer it into an area with plenty of salt, crystal, or metal. Continue to hit those until it's knocked out. The high levels WILL take a very long time, and speed also seems to be a factor. If you go downhill, it speeds up, and if you hit something when you are faster, it gives more torpor. For optimal torpor, try and get max downhill speed and hit metal.