With my ilustrations, i paint the entire thing (very basic) with one layer. Then i gradually add details, refining them on multiple layers as i go. I dont usually use more than 5 or 10 layers, and thats including a scan of my original sketch. So give less layers a go. You'll find it much easier. The less layers used, the more risks you take. It's good to take risks.
Also, thought id point out, when you are happy with how something has turned out, (lets say you used 10 layers) merge them together. Your computer will run faster and you have more control with the overall piece.
Not half bad. There's something bothering me with the overall look of the surfaces, but since I cannot put my finger on it let's not dwell on that. Like perhaps I should not even bother mentioning this because I can't figure out myself what I want to say.
Though, 300 layers? My stuff usually has 5-7 layers, between 10 and 15 in most extreme cases. Mind cluing me in on what the heck?