You don't need Cherub Rock to be able to play CDLC. If you already bought a song, then that's good. If you haven't, then go get Cherub Rock, save yourself some time. Anyway, there is a program in which you change the ID of CDLC. It is called Rocksmith Toolkit GUI. You can get it here: http://www.rscustom.net/.
1. Download the file.
2. Open it.
3. Click on RocksmithToolkitGUI.
4. Once you have opened the program, go to the 2nd tab on the top (from left to right).
5. You'll see that there is an option to choose a song. Choose a song which you have bought, then click on 'Choose DLC'. Choose any CDLC you have and then, voila, you may now play it!
For a more detailed tutorial, go here: