Hello pownstar!
You don't mention the type of juice - Darker, sweeter juices can gunk a bit more quickly. Also, higher VG can tend to gunk you up as well.
If I'm not mistaken, the STP is a 7mL tank? Are you still on your first tank? If you're into a 2nd tank already, it's possible that it's time to change the coil....
Did you happen to prime the OCC before trying to hit it? I make sure to put a decent amount of juice directly on the wicking (side holes and top) and then I'll start low and gradually work my way up. It's possible that once the cotton has been singed, you would either have to replace the coil or at least rewick with fresh material.