I run a plastic single edged razor blade down against each side between the calk and the item. If you cut it deep enough you can usaully just grab one end and pulling gently get 99.9% of it to just come off in one chunk
Not sure what's in it but at just about any home hardware type store they sell silicone remover in the same section as the silicone. It usually comes in a small bottle with an aplicator brush.