[MacDV] Editing Voice over in iMovie

[KS]

It's been a while since I've been asked to edit a training piece on 
iMovie with voice over.  I seem to remember that if you want 
transitions like dissolves, etc.  there's some "trick" to editing so 
the video and V.O. don't get out of synch.  I believe it has to do with 
adding frames to compensate for the amount of scene you lose when 
applying a transition.

The last time I tried editing with V.O. I had the video and audio 
synched perfectly – then when I applied dissolves and fades throughout 
the 10 minute piece – the whole movie was out of synch.   After many 
attempts to fix the synch, I gave up and took them all out.  The result 
was a "cuts only" movie.

Is there a simply way to compensate for this synch problem when you 
want dissolves and other transitions throughout the movie and still 
have everything in synch?

Someone told me, "just add a couple of frames on the back and front of 
each scene."  But, that doesn't give me a step-by-step process to 
follow.  I would really appreciate a more detailed "how to" on this, 
please.

Thanks in advance,

Karl