You can also diffuse your key light source. Piece of 251 or 250 (photographic diffusion gels) - these can even be temporarily taped right onto your light source - the loss of light will be minimal but effect is very pleasing and can be easily controlled by varying distance from the light or to the object. If you are using light source that gets very hot (halogen or similar) - you will need a bit of space between light and gel. Or you can bounce the light onto your object, instead of direct lighting, this can help in avoiding unwanted highlights in reflective objects.
So many options for this... you can also tape a white tissue or paper towel over the light source to act as a diffuser and reduce glare and hot spots from reflective surfaces.
Sure can, just have to watch your light's heat - gels can withstand quite a bit of heat (and moisture) and one can re use these for many years - and are pretty cheap. Old pieces of bed sheets are good too, so is bleached muslin.
Lightly misting hairspray on picture frame glass, can be used to copy photographs without taking them out of the frame.
It should work on other shiny objects too.
Not tried it but worth a shot.
Easy cleanup with hot water.