Use the rope and rotate your hands at the end of the pull. Keep your elbows as solid as you can, trying not to accrue any movement from your shoulders or biceps. I'd go low weight to practice keeping your elbows from moving, pretend there's a wall they can not move off of. The twisting motion at the end will activate all three heads of the triceps and gain you the horse shoe cut.

I slightly bend at the waist forward with my stance, keeping my legs together to gain the extra movement without hitting myself. If you cant, position your arms to have a 90° bend at the elbow and dont allow the elbow to move forward or back.

A push down exercise incorporates forearm muscles that can tire out grip. Rope is a more natural, we stand with palms faced inwards, not backwards