Here is what I did - thanks to the other guides for this achievement as it made things a lot easier.
You will need:
1) Mic - wired is better since batteries do run out
2) Turbo controller
3) A timer
4) Completed all vocals locations in career mode so that it defaults to the "Singer Wanted - USA" venue.
5) Free DLC songs Grave Of Opportunity and On Broken Glass.
6) A fan.
1) Set the mic up to the fan.
2) Go to the Singer Wanted venue in career mode and select Grave of Opportunity, On Broken Glass and No Sleep 'til Brooklyn.
3) Have your turbo controller spam the A button.
4) Set your timer to 13 minutes 45 seconds and start it.
5) Walk away until the timer rings. Come back and you should be at the select song screen for the Singer Wanted venue.
6) Repeat steps 2-5.
You make $1940 per set I believe (you don't get the no star power used bonus). I chipped away at this over the course of 10 days making about $50K per day while doing other things. I realize this won't be for everyone and it is a little slow but it does work.