The kush got me higher than an old hooker's skirt
Mack is comparing his high to a hookers skirt to show the level of his high. A hookers skirt would probably be lifted pretty high, higher than what a skirt normally is. Meaning, Mack is very high.
To help improve the meaning of these lyrics, visit "First Place Winner" by Lil Wayne (Ft. Boo, Curren$y, Mack Maine & Swizz Beatz) Lyrics and leave a comment on the lyrics box