How to ignore faulty instrument readings in glass cockpits? When an instrument fails in the cockpit, it is better cover it with something, either a dollar bill or a gauge cover (if you happen to have one of those), so we won't accidentally process the information from the faulty reading. My instructor taught me to literally smash the gauge, so the status of that instrument is not in question.

This works well in cockpits with rounded gauges. Nowadays, more and more GA aircrafts are fitted with glass cockpits. Obviously I can't just smash the screen, or else everything will be gone! What are the steps that one can take to avoid reacting to the faulty reading?
Like in a steam gauge cockpit, you can put adhesive INOP stickers on parts of the glass panel. Stickers for the Garmin G1000 are available commercially, and I had to use them extensively for my instrument rating.

Keep in mind, though, that glass cockpit aviation systems will detect a faulty sensor automatically, and the faulty instrument will just appear X-ed out (like the picture on the INOP sticker) instead of showing wrong values.

But even multiple sensor source cross checks doesn't keep you safe from misinterpretation. See Birgenair 301 accident for example.