How about using ACETONE to soften it and then with a razor scrape it off?
I did it this way when I removed /re siliconed my 100 g.tank ,but you can only put a little bit of acetone at a time and very quickly before it evaporates ,scrape the silicone off.
A razor blade will NOT get silicone residue off glass. Neither will any of the commercially available "silicone removers" that can be legally sold in the US.
Abrasion (in the US) is your only way of really getting it up. I found a most efficient method of accelerating the removal process is with the cloth polishing wheel of a dremmel tool. Maybe a cloth polishing wheel of any high speed drill would do as well.
Use a razor (changing to fresh blades OFTEN) to get up anything you can feel with your finger tips. Then use the cloth polishing wheel to remove the (otherwise impossible to remove) visible residue. Then hit it with copious amounts of acetone to float up any thing that you cannot see, wipe clean with a lint free cloth and let dry.
That's how to get silicone off glass legally in the USA. Some other countries have some other chemical (and highly toxic) options.