Painting on Selected Faces

[BackStabberAssGrabber]

Hey Everyone. I'm trying to paint a pair of sunglasses for my character. The idea is to paint the glass portion with a highly reflective material and leave the rest as a single plastic / rubber like material.

I'm trying to paint on selected faces. So I select Geometry Decal and start highlighting the faces i want to paint. The face selection doesn't really do anything because the selected faces and the unselected faces are painted all the same.

I then tried masking using the face selection tool by Pressing T to quick mask then highlight the faces i want to mask with no progress. Am I missing a step or is there no way to select the exact faces you want to paint?

[僕の名前 (仮)]

Add mask and use geometry decal on that mask.

[BackStabberAssGrabber]

Thanks for the tip. I was painting my mask instead of creating a mask layer. The mask layer is key!