Originally Posted by
himespau
I've had the same issue using Park Tool Grease. Using the appropriate sized seatpost (unless it got reamed bigger somehow, or the post is abnormally small) and I clamping the post to the point that I'm afraid of permanently bending the ears and I still see a little slippage, so I'd love to know the answer as well.
I often use carbon paste on my seatposts regardless of what the post or the frame is made of. It allows for proper clamping without slippage using less torque.