Skyscanner was mentioned in the video. I personally have used it for years; particularly, it is very useful when booking international flights. The only drawback is you have to try different date combinations to see if the fares are lower on a particular day of the week.
Another idea mentioned in the video is to book directly with the airlines. This is true because some low-cost carriers do not publish their fares on the aggregators such as Google Flight or Expedia. If you have a loyalty membership with an airline, sometimes you don't earn the mileage through the 3rd party website where you purchase the tickets.