Ages ago, the clippers I bought had an instructional video that came with. I used to cut all the kids hair when they were little...cost them only a kiss!
What would happen if you looked on ebay to see if you could find a video/CD for sale there?
Here's one about giving flat-tops!
eBay: Flat Top Haircut Instructional Video (item 280090200454 end time Apr-03-07 21:34:33 PDT)
There are others listed under a search of 'haircut video'.