This stuff is dangerous as hell and you can't use it indoors. The problem is, HCL is actually a gas and it's savagely soluble in water to the point if you have a bottle of the concentrated acid (just HCL dissolved in water) then as soon as you open the bottle fumes escape and reach with the *moisture in the air* to make microscopic droplets of hydrochloric acid, that's airborne. You never forget that smell and you don't ever want to smell it.

Outside. With goggles and gloves and either a leather apron of equivalent. If you get this stuff in your eye you'll be begging for somebody to kill you. It's not terrible just in your skin, but you never do anything with this stuff unless you have an opened box of baking soda nearby which will neutralize it 100% instantly.

For a long time since it was first published the Guinness book of world records listed this as the worlds strongest acid (its been replace by some Star trek sounding stuff) but it will do a better job on that glass than anything on the planet short of polishing it off with cerium oxide (which is not quick).