Computersight -

To start this off, I used Photoshop CS3 but any version will work the same.

1. First find a base picture that you would like to change the front bumper on.
2. Create a new layer and draw out the body kit using the line tool.  Pick a color and a line width that looks good.
3. If you know how to, use the pen tool or you can just use the selection tool.  Select the whole outside of the body kit that will be brushed then fill it all in a color similar to the base color.  Make sure you fill it on a new layer.
4. Using that same selection from step 3, subtract everything from it that will not be a highlight color.  Then fill in that selection on a new layer with a color for the highlight (lighter color).
5. Similar to step 4, use the selection from step 3 and subtract anything that will not be a shadow.  Fill in the shade color on a new layer.
6. Now if you have any vents or holes in your design, which you should for realism, select them and fill that in with black on a new layer.
7. The easy part is now done.  At this point you should have a base color layer, highlight layer, shadow layer and a black fill layer.  The bumper will look very flat right now because they are only solid colors.  This next part takes lots of practice and patience so i suggest making a back up(duplicate) of all the layers in case you mess up.  Just turn those layers off so they don’t get in the way.
8. For this tutorial, I am going to use the Dodge/burn tool.  In order for this tool to work, you have to be on the layer you want to change which is why i suggested duplicating them.  Also have it set on midtones and the exposure set really low, i used 6%.  The dodge tool will lighten up the areas and the burn tool will darken.  This tool can be sensitive and if you don’t like how its turning out, the undo button can be a good friend.  Just keep practicing and you will figure out if this is the right method for you.

Below is the picture tutorial:

(All pictures taken by me)

I hope you enjoyed this tutorial and that it was easy to understand.  Feel free to leave comments telling me if you liked it or how i can improve it.