I just picked up some stuff to remove glue/silcone etc call Pro Strength De-Solv-It
Contractors Solvent
It is a natural based product, can be safely used on acrylic (I needed to take sticky letters off acrylic) Let it sit for 30 min-1 hr and all the glue just wiped off.
Supposed to work really well for silcone as well
so yes, razor blade for most of it, and something like De-Solv-it for the residue