I'd like you meet my two new best friends. They are called Burn Tool and Dodge Tool. I knew of their exsistence a month ago but I seldom used the burn tool and never the dodge tool. Now I can't imagine how I got by without using them. It's amazing how many details you can 'paint' on a plain flat color, like all the shadows and highlights on these flowers.
Oh and perhaps this is a good time to mention an old best friend, my Wacom Bamboo Fun pen. I almost gave up using it when I first got it, didn't really think I could control it but these days I've totally given up on a regular mouse and use the pen all the time. Another big help in these design attempts.