Yes, there is an easier way. Play the Capture tracks back to your mixer, make a nice mix-down and record the stereo sum (master) of each song in Capture again (tracks 25+26). If you mix 20 songs like this, you will find 20 WAV files (Stereo) in your recording folder, which need to be named (titles of the songs). If you are using Studio One Pro you can master those mixdowns and "publish" them as MP3 files or any format you choose. Or you convert the files from WAV to MP3 in an appropriate program. Capture can only handle WAV files.
It is indeed a problem, that you can spend a lot of time on mixing the songs. Musicians tend to not listen to the songs/mixdowns very carefully, so try to keep your work and time as reduced as possible. Another "trick" is to mix only two or three songs and see if there really is a need for more. ;-)