The main key is to take it slow. I haven't watched any professional DVDs, but from my experience, I found this worked:
Get the pup used to the buzzing noise when the trimmer is on (near the pup but not on the pup) > then get pup used to the vibration somewhere on the body (touch pup on their back with the vibrating handle, not the shears) > gradually increase the time of the vibrating handle on their body, then along their body > then start small and actually use it to trim a very small part of the body ... gradually over several days and several sessions, with lots of treats.
This is how I went about getting my two used to the trimmer for just their ears and paws. As soon as they freak out, I stopped. When they accepted it, I give lots of treats and say good boy good girl.
Because I'm growing out their coat, I use scissors for the body. But it's still the same - take it slow, lots of treats, and of course them knowing the "stay" command comes in handy.
