What's the best and easiest way to apply good quality silicone, which I'm told are never the water-based types, to freestanding glass and ceramic tiles in showers? Can I remove it with a razor blade if I've already overspread it?
Use masking tape to prevent overspreading, and dip your finger in mineral spirits to smooth it out. Remove the tape before the silicone sets. Never use water to smooth silicone, only latex/acrylic.
It's difficult to remove silicone from rough or porous surfaces. No problem to remove with razor blade from glass.
I would like to add that cleaning the surface with denatured alcohol prior to applying the sealant is absolutely critical. Otherwise you will begin experiencing separation with in a few months.