A fairly decent training video from BoxingPerformance.com that runs you through a focus mitt session for a 5 punch combination. Two things to point out:

1. If you are the mitt holder, and are going to work your fighter's defense, don't swing in an arc over his head causing him to bob. Swing in a straight line and REALLY make him bob.  Make him really use his legs.  Does no good to loop a swinging punch over them, their opponent isn't likely to do it.

2.  BoxingPerformance.com is a pay site.  Went there for a visit and couldn't access anything without paying $9.95/month.  Not that that's bad -- they could have some decent stuff, just wasn't able to access any of it to to tell you about it.