Reddit mentions of Digital Painting Techniques: Practical Techniques of Digital Art Masters (Digital Art Masters Series)

It's very photoshoppy. The problem a lot of artists have with photoshop is that they tend to get too sucked into details and lose sight of the bigger picture. One of my professors describes it as 'painting a highlight on the eyelash of gnat.'

Painting in Photoshop is no different than painting on a canvas. You should start out loose and transparently, block in objects and build them up slowly. There is no magic button that just makes your stuff look good, it takes the same amount of skill as mixing paint and applying it with a brush. I'd suggest going to places like http://www.imaginefx.com or http://www.cgsociety.com and looking at other peoples' art and tutorials on how to paint.

Try converting your image to black and white. The human eye sees two images, one that is just lights and darks and one that is color. Color is totally arbitrary, if you painted a solid black and white image of a teapot, you could then make that teapot any color you want so long as the black and white core is unchanged. Every color has a value, yellows are closer to white and blues and reds are closer to black. Contrast is how you draw the viewer's eye to where you want them to look. Always have a center of interest in your painting. Don't bog yourself down in details, squint at your reference and really ask yourself what big shapes you see. Only some details are visually present, like looking up at a skyscraper and attempting to draw it - not every window is important, the effect of repetition is. You can suggest detail instead of being too rigid with it.

If you're not using a tablet, painting in Photoshop is tremendously difficult. Tablets are pressure sensitive digital pens that you plug into your computer which allow you to make strokes that get thick and thin or that vary their transparency. If you're serious about it, I'd suggest looking into it.

Painting is not easy. If you really want to get good, you need to learn from good resources. I just picked up Master's Collection Volume 1: Digital Painting Techniques and it's a wonderful resource. I'd recommend checking it out if you are interested in getting better. Copy old masters too. Just remember that art never comes quickly, it's a slow, laborious process that can takes years and years to get good at.

Keep on trying, nobody ever improved by becoming discouraged.

I actually just recently got these books, they may not necessarily be what you're looking for but these have been absolutely informative to me

p.s I checked these out of my local library but I'm hoping to purchase these soon.

Drawing on the Right Side of the Brain

Digital Painting Techniques

Make Great Art on your iPad