Hey bro, dont get discouraged, brushing takes a certain amount of time to master and everyone struggles with it at first. First of all make sure you are selecting shapes on new layers, then try this.
Select your shape and fill it with your base color, use the eye dropper to grab a color from your original picture. THEN with your selecton still active, open a new layer above your fill shape. Grab a good sized Soft brush. Size it so its almost as big as the height of your selected shape. Select a slightly lighter color using the eyedropper again. Set the brush at one end with half of it off the top of the shape and pull it as evenly across as you can from left to right. Take a look, if you dont like it, step backward and do it again. You can adjust the opacity, use blur tool to smooth and blend colors together and even change layer properties for different options here. Once you get down how to graduate colors effectively you can actually do this all together on one layer, but this way is good practice and allows you to go in steps, making it easier to correct.
I have been meaning to make a tute on brushing and have one in the works but honestly there is so many variables that come into play, its extremely hard to make a tutorial thats not either too generic or too complicated to actually be worth a darn. It simply takes a lot of practice and its really exactly like coloring or painting. The most important things to keep in mind are: use colors straight from the car and in the general area where selections are being made. Study the car, specifically the body lines and contours and make shapes that flow with the design. Use layers effectively. Dont expect to do everything on one layer. Work from dark to light. When you get a particular body part finished, Merge all layers together then you move on to adding highlites and lowlites with the burn and dodge tools. ALWAYS duplicate a layer of the part right after you merge, just in case you screw it up !
Most choppers arent ready to tackle brushing after chopping for only a month so, nail down those basics and give yourself some time to develop and have fun. Putting too much pressure on yourself can be frustrating and counterproductive.
Keep trying bro, it'll come together with a little patience and plenty of practice.
