5. Scraping
As mentioned, it is possible to buy toothbrushes that include tongue scrapers on the back. Using this regularly can help you to improve that aspect of your oral hygiene and thereby to avoid getting a white tongue.
At the same time though, you can also use scraping in order to immediately address the problem in the short term. If you check yourself out in the mirror and you notice that your tongue looks very white, then you can quickly scrape it off in order to solve the problem. Just be aware that in some cases, it might actually make the problem worse if it means that you create dead skin around the top of the tongue.