I have used a large straight screwdriver to open up the channel- slowly working along the channel. I want it just a little loose. Then run clear tape along the glass. The tape should wrap around the bottom. I try to make sure that the tape will cover the paint just slightly above where the channel will cover. If needed layer a couple of extra pieces of tape for a slightly snug fit. I would avoid any type of hammer or hard object to pound with.
Good luck snd take your time.