This is the way i got the achievement today:
The easiest one is definitely the bass-career. Like in the other solutions discribed you only have to play through the free gigs.
The hardest one is BYOB and I tryed the song 20 times failing at around 15% in the first verse. Insteed of wasting time practicing I used hyperspeed on level 3.
For hyperspeed go to 'options', 'cheats' and use the following combination:
Green, Blue, Red, Yellow, Yellow, Red, Green, Green
Than turn Hyper-Bass to Level 3.
Back in the career I was able to get through BYOB in one try. The verses are very easy now. You can better get in the right rythm of alt-strumming and for the green and red frets just tap the buttons very fast. Before hyperspeed I was not even able to survive 5 seconds in the verses but now it was the simplest part for me.
But the intro is now a bit harder than before, so if you fail it, don't worry. You will push the rockmeter in the verse. Between the verses try to get as much starpower as you can. In the song are two parts which are really hard and the only way I survived them was because of the starpower.
As I finished BYOB the achievement poppud up, so don't worry about the "cheat". If it not pops up, play 1 song in the song-overview (the door to the left of the last gig). An easy workaround if its glitched for the first time.