Doug,

Get a medium grit emory cloth, or use 180/220 grit sandpaper. In my experience, you can not rough up aluminum or glass too much (well, in the realm of common sense at least).

I only use the Scotch brite pad for slate, which is softer and hence, needs less abrasion to create an uneven surface.

EDIT> you say your calls are whining...are your strikers getting glossed over? Have you tried switching to an acrylic/synthetic striker to see if it's the striker or the call?