Think I found the tutorial that says about what you said.
go through ACW for the chords of the audio file.
Choose a style and save save in a ut folder with a unique name "guitar ballad 120"
save 5the sgu to that folder with a name like guitar ballad. Then do that again(ACW,etc) with the next file that you transpose and save it as guitar ballad +1(transposed up 1)
Do it again with next audio save as guitar ballad +2(transposed up 2).
These are all saved in the same ut folder.

Make sure you're audio level and tempo is the same for each track and sgu.
I've messed around with this enough to see it should work well. There's some good solo backing tracks on youtube that are public domain that should work well
http://www.youtube-mp3.org/ is an online mp3 extractor for youtube audio.
I might have missed a step here or there but think it might be close.
Wyndham