I'm stuck on Holly Summers (on Mild difficulty). After several failures, I quit the mission and went and searched the city for money and Lovikov balls to upgrade my katana and learn all the wrestling moves. When I started the rank 6 mission again, nearly every enemy I hit was stunned, and I killed 90% of them with wrestling moves. I don't know if this was because of the new katana or a Lovikov technique, but it made things a lot easier.
I'm not getting wrestling moves off against Holly any more often, though, and I don't notice a pattern. Is there a way to consistently stun her so I can perform them?