Lip Sync with 2 or more characters in a scene

What is the best way of using the auto lip sync feature if you require 2 or more chaarcters in a scene?

• Currently I have one character and sync'd his voice to the audio.
• However I want a conversation with another character.
• What's the best way to organise a scene for multiple voices? Is is to create short audio files with each person's line from the script - then create new layers with each seperate audio file and mouth graphic clip to auto sync the instance to each line? Am guessing this would quickly result in scores of layers and audio files in a few minutes.
• Wondered if there is a better way to do it?
• Or is there an open source .FLA anywhere to download that shows how to set up multiple voices in the same scene?

Thanks!