What up, Polynomial. I can't seem to stop pulling with my arms on those power cleans.
What helped me was to continually think about not bending my arms during the pull.
I tried thinking a bit about the physics of the movement and I think that it helps in understanding of what's going on. So for now, forget about the power clean and consider a vertical jump: the force that propels you upward is generated by your legs at the floor. Once you're in the air, you have no other force acting on you except for gravity.
The power clean is similar in that the force that acts on the bar that sends it traveling up is transferred from your legs, through your trunk, and then through your straight arms to the bar. Once the bar is initially propelled upward, the only force acting on it should be gravity. As the bar is flying up, you can relax your grip and easily rotate your arms and catch the bar on its way down.
I guess that what you could theoretically do is at the top of the second pull (when you jump), just let go of the bar. It should fly up, then you can try to catch it, but I suppose that people prefer to keep their hands around the bar for some control
At least this is my current understanding, and it might be totally wrong.
Edit: Oh yeah, and also, pulling up with your arms is essentially trying to do an upright row as the bar is traveling up. Well, even though it's traveling up, the only force acting down is gravity, so you're basically trying to do a 265lb upright row. My guess is that people can power clean a lot more than they can upright row, and my point is that after "jumping" the bar up in the air, any sort of arm pulling isn't really adding much to the distance that the bar travels up.