People who excel at any skill use a technique called "deliberate practice" whether or not they know they are doing it. Deliberate practice can include any or all of these steps: planning (organize work in a structured way), concentration/dedication (higher attention span), repetition/revision (strong tendency to practice), study style/self reflection (tendency to self-regulate learning).
A rap related example from an article I just read:
"B.o.B. would practice rapping by writing out DMX’s lyrics on a sheet of paper, then hone his rapid-speech skills for hours. When he wasn’t reciting DMX’s words, he was crafting his own, sometimes in church, sitting in the pew while his father preached."
Hope this helps.