How to wash your hands precisely and thoroughly

The Hong Kong Centre for Health Protection's Recommendation to Perform Hand Hygiene Properly (2020) gives a detailed procedure for how to wash your hands. If you want decent hand hygiene, just follow all the directions there. They're probably similar to what you're already told.

If you want to be precise and thorough in your handwashing, some studies will give you more details. Shi, O'Donoghue, et al (2023) did a nice observational study on how washing technique affects cleaning results. The study uses the same seven steps of scrubbing as the Hong Kong Recommendation. Figure 2 shows the estimated washing effectiveness as a function of the duration of each step. If we take the peak of each such curve, we conclude that optimal handwashing goes like this:

1. Wet hands
2. Apply soap
3. Rub palm-to-palm, 4 seconds
4. Rub palm-to-dorsum, fingers interleaved, both ways, 6 seconds
5. Rub palm-to-palm, fingers interleaved, both ways, 2 seconds
6. Rub backs of fingers in palms, curled together, 4 seconds
7. Rub around both thumbs, 5 seconds
8. Rub fingertips in palms, both ways, 6 seconds
9. Rub around both wrists, 6 seconds
10. Rinse
11. Dry

Here's a video to nail that procedure.

The compression artifacts are terrible, but it's still clear enough to be usable. I may have overestimated the time for getting hands wet, rinsing, and drying.