First I found few reference images, and in Photoshop I have drawn basic shape of Mini Cooper. I am using vector tool in Ps 'Pen Tool' for drawing shapes. When you finish your path as shown on picture go to Convert Point Tool smooth your path, then right click on path and choose Make selection. Fill it with color.

Using Pen tool make new selections an draw rims and roof. To place shines and shadows create selection and use Dodge/Burn tool (decrease hardnes).

Draw tires, place shadow, and create very rough shape of interior.

Now create mirrors grill and chrome parts. To draw chrome, create selection, fill it with bright gray, than use Dodge tool, Burn tool, and blur all a little with Blur tool.

Do same like in previus step to make lights. With white brush (0 hardness) make glass shining.

discuss this topic to forum