Well the reason I asked was to first find out what kind of tutorial would suit you. there are many resources on the web for digital painting a few good places are cgsociety, gnomon workshop and Dart(digital art tutorials) these sites many deal in dvd's and well worth the investment
but one major tutorial that many people ignore is auto painting itself. the process auto painting uses is pretty much the same process artists use in traditional painting.
watch how painter blocks and lays in the major or dominant colors first
then refines itself slightly it's still not detailing but it's laying in secondary colors which defines more of the hues,saturation and variation of the hues or darks and lights still it is not getting bogged down in detailing
the final stage is detailing drawing in or tweaking areas. but that's basically how to paint to many start with the detail and become afraid of losing it in the the process of painting that's why so many people use too many layers because they are detail oriented. use color to shape up the work and the detail will present itself
it's kind of like writers, most writer's begin with the last line of the book and that's what detail is to painting the last stage
so you need a large brush to lay in the basic shapes of color, a medium size brush to place the secondary colors and a detail brush for detaing you can use any medium dry or wet.