An atomic bomb your threat if you survive the bomb itself is fallout which is just dust. So any method that removes dust is sufficient like dish soap water. This video is more about chemicals threats. What you use greatly depends on what exactly the chemical is. Roughly though, the "solution to pollution is dilution". If you rinse someone with a ton of water aggressively you are bound to get most of it off, however it is very inefficient. Your threat is more oily substances so degreasers are often used. Biological threats are simpler but require much more discipline due to cross contamination issues. Bleach solution is pretty much what you need, but stuff like the covid regulations with thing like masks and "social distancing" isn't a real thing and doesn't work because of cross contamination. Lots of companies publish ERGs which basically is like a dictionary on how to decontaminate various substances.