Keing any reflective surface is a challenge and almost impossible if the shoot was not well thought of in advance. The object needs to be far from the chroma background, with enough variety of other objects/color or black and white surfaces to eliminate any chroma reflection. Rotoscoping the object is the way to go. Mocha can help, but I would give Roto Brush a shot as well.
Tudor “Ted” Jelescu
Senior VFX Artist