worldizing is probably your best bet. transmit the audio through some hand-held CB's and record the output. Also, the type of sound will depend on the 'fake' modulation - FM will sound different from AM, SSB etc.
Before mixing, you need to learn Dialogue Editing.
A good reference Dialogue Editing resource is the book by Purcell "Dialogue Editing for Motion Pictures". Bit dated in terms of the technology, but the principles are sound and lasting.