what are you using for a primer? It looks like you are getting an uneven finish with your models. I'm sure you are aware that there is much to learn when it comes to painting, but getting the procedure/process down is the first step. Even if you haven't acquired a lot of experience with techniques like washing and such, you can still improve your models by following a good tutorial on the basics. I'll see if I can't find an example for you.
Automatically Appended Next Post: Here's a link on painting with washes. Personally, I haven't done it this way, but it is simple. Notice how without so much as touching the details (teeth, bullets, etc) they still pop because of the properties of the washes. The key to all of it is successive thin layers, each with a purpose, but none over-done. That is where the base coat makes a difference.
http://warhammer-figure-painting.com/2011/07/warhammer-40k-painting-tutorial-orks-with-mostly-washes/
Hope this helps! Keep at it and always ask questions if you aren't sure.