I have used my Zoom h2 feeding into my sender unit of my wireless lav unit and set it hidden on a table to record a group discussion, I have the Adzen WR -pro unit which cam with a lav mike and a hand held mike with a standard 1/8 plug in for external mike. I set the Zoom for 360 degree sound recording pattern and plug the receiver into my camera and start recording I will use my other cameras to record ambient sound. If I need to mix the sounds I extract the sound with AOA Audio extractor and then mix and balance the sound in Audacity, export the final sound track and plug it into my time line . AOA and Audacity are both freeware and using a n audio tool like audacity you can have complete control over sound balance, volume per track etc.
