Kyle Goetz said:

A quicker recording method with Audacity is to record each line as a different track   without saving each line one-by-one and then removing it and starting a new line. Instead, record a line. Then hit 'stop' and then record the next line. Audacity should begin the new line as a new track. Do this for each line, and eventually you will have an Audacity project
with, say, 39 tracks, each a different line. Then File->Export multiple, and it will export a
WAV file for each track. You can even specify a naming convention, which means you don't
even have to rename the files before uploading.

My addition: 

Just make user that you don't submit your audio as one large file - the Acoustic Model creation scripts are not set up to handle multi-track recordings.