If I understand you correctly, you are slightly confused about the procedure. The only part of the housing that you paint is the outer part. The outer part serves no functional purpose other than to look good. The inner part near the headlight bulb is left unpainted and thus does not effect the beam's spread. However, I believe the paint that westcoststyle used on his reflectors would have the look you desire. Look for a transparent tinting spray (like this) at a hobby or possibly automotive store.