You are an amazingly talented person, my friend. Coming from someone who adores Bob Marley and someone who is utterly impressed with his life and the work he did... You captured his spirit in this painting. Congratulations. I really have no critique to offer you. Just a pat on the back. This is a great painting!
It was made on photoshop with a 4x5 tablet, just one default brush I only tweaked when needed. Besides that... Hey, I'm about to make a "wannabe" tutorial, showing the way I work, maybe that's more enlightning... come back in a couple of days!