Yes this one, for doing better and precise outline of the bodykit try to use the pen tool:
- select pen tool
- go to Path label (usually is placed in the same window of Layers and Channels)
- create a new path
- trace with the pen lines (take a look in some tutorial site for learnig how pen tool works... and remember that if in future you wanna work with Photoshop this is thing you must know)
- now select a round brush size 1 pixel red color... select again pen tool, click on the path you've done, make a new layer and click to right mouse button and select "Stroke path"
Is more difficutl to explain that doing that
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I tell you that because looking at the front bumper I see square lines even where proabli needed rounded lines.
Anyway try to continue, every chop is a little step for you skills even if is not good or full of error (after lot of year I do even now mistakes... lot of them!
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).