Good advice...
If you open up in zone, you can wait until the defense shifts to audible to man. It gives your opponent an initial pre-snap he'll use to change his plays, then you switch coverage at the last moment. The drawback is failing to audible to the coverage you want in time.
Personally, I like to blitz with the linebacker they are attempting to beat in coverage, and manually defend with a player with better speed. It gives them the notion that they have the matchup they want, but can lead them into a hasty throw into coverage.
Mix a zone in with your man coverage to the spot the ball is thrown. It shrinks the window the QB can deliver the ball and forces opponents to go somewhere else.
Last but not least... Play zone and manually audible a defender to play man on the receiver.
All are decent techniques, but the best one of all is the one Phant gave... For years and audible has been the best way to cancel out any oddities that happen in man coverage.
Later