Are you brush painting or using an airbrush,the thing needed is practice,practice,practice.Do you have a particular scheme in mind ? Most are tri-color,Dark Yellow,Red Brown,and Olive Green.I airbrush my schemes freehand,if you are brush painting,you can freehand or use masks.When I airbrush a tri-color scheme,I tie it together by misting the basecoat over the whole thing,or a filter will do this and also tone down the contrast in colors.It's difficult to answer in a short post.This site and others offer publications on basic modeling techniques,perhaps try them.I hope this helps some,I'm sure others will also chip in.