Synchronize and combine two Audio vocal tracks

Hi guys,

I have two seperate lav mic recordings of two people, one is the interviewer and the other is the interviewee. I have synched the tracks together in premiere pro and sometimes there is no reverb but sometimes there is and it sounds echoey/tinny. 

How can I combine the two tracks so that it only uses the audio when the person is speaking and vice versa for the other track? Obviously I will want some volume on each track at both times so that the levels aren't up and down and you still hear the ambient noise but what is the best way of doing this in audition or premiere pro?

Thanks