Painting Scopes and Lenses

So after priming and zenithal highlighting— after contrast/speedpainting, how do you Brothers go about painting things like: weapon scopes, targeting lenses, the magnifying glasses apothecaries have equipped— basically anything that would emit light, be observed through, etc? Friend of mine gifted me something called “Ardcoat” and (fairly new to this hobby) I figured I’d undercoat anything with glasses or lenses with a base white, followed by some kind of paint thinned down with Lahmium medium of contrast medium? Thoughts?