I do it 2 different ways... Mask and Spray, or lattely cut strips and apply.
I use regular tan masking tape:
1. Get it down good and tight
2. You will see the ridges where the frame is, cut that away with a new x-acto blade
3. Cover or mask inside as to avoid overspray
4. Lightly Spray Paint
5. When dry, remove tape and "Voila"
Example of painted "aluminum"
Example of painted "to match color"
Example of applied tissue paper of same color
Hope that helps...M