Hi, guys. I've been trying to paint "The Simpsons" characters with acrylic on illustration board. The problem is the color doesn't clean or smooth after I paint. For example, I painted Homer's face with yellow acrylic color but some part is more darker than other area or some part is more opaque than other area whether I add the water more or less. Can you get the idea? It's kinda hard to explain this situation. However, what I'm trying to do is I'm trying to paint just like the frame from The simpsons cell animation, very clean and plain color. No smudges, no stains, no spots and no opaque!! Could you please help me!!