Patience. Go through all the motions you did with the other two, and pick a specific expression. Leo is the most iconic and different looking of all the turtles in the flick. Don and Raph are pretty similar when you really get in close and ignore the color of the headband - with several key differences such as the curve of the upper lip, where Raph's go up, and Don's for the most part goes downward into a slight point.THANKS RM & TMG!
Looking over these make's me want to start now!
Already a very good likeness. What's interesting about Leo is his slight snub nose snout indicated by the red lines. Very good so far.