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Position the blade of the razor where the caulk meets the glass. Apply pressure to the razor and begin scraping off the caulk. Be careful when using the razor, so you don't scratch the glass or cut yourself. Set the hot air gun to a high heat setting and point the nozzle at the trouble area. After a few moments, test the area with the scraper to see if it has softened enough for you to continue. Scrape until the majority of the sealant is gone. If you don't have a hot air gun, a hair dryer on the highest setting will work just as well. Dip the sponge in the rubbing alcohol or mineral spirits and gently wipe the glass. If there are still large bits of caulk, try applying heat again and go back to scrapping. After all the sealant is removed, dip a cloth in rubbing alcohol to get rid of any cloudiness on the glass.
Use the razor to begin scraping the sealant off the glass surface. Apply heat with a hot air gun if the silicone does not come off easily with the razor. Remove any leftover sealant with the rubbing alcohol and sponge.