I'm quoting Bstringbean's comment from the other solution
"You can't get this during the third stage boss because the copies it sheds dodge your boosting. I got it when I was going for the Congratulations on your driver's licence! trophy playing the first level on rookie difficulty. Right before the end of the level where the boss spawns, a good amount of ships will clump up into large groups following you.As JustSurvive said, dodging for a few seconds and letting them build up allows for easier completion of this tropy. Also be sure to use the Nemesis ship because it has significantly more boost than the other ships."
End quote.