So, I think I should describe how I export songs... You highlight the region and tracks you want to export and then File > Export > Audio.
A dialogue opens and you can set some parameters like file name and bit depth etc. When making a CD, I export 16 bit Wave Files.
Now, with this known, how do you prep a track to be the right length etc... What I do is select the range of the song in ruler area (usually I add markers to the ruler at the beginning and end of the song). I select all tracks, and click in the ruler between the two markers selecting the Range. Then I execute a Tracks > Bounce to Tracks. If it's the first song of a night's jamming I let Bounce to tracks create a new mixdown track. Otherwise, I keep using the same mix down track. After it is bounced, I add fading and trimming to the ends of the songs track. I make sure the mixdown track is routed directly to the interface and not to the master bus which has fx on it. Last, I click on the Clip and choose File > Export > Audio.
This way, if I want to shorten or lengthen the clip a little to get the right distance between songs, I can easily come back to this point and make the tweak.