For the most part, years ago they had you list your prescription meds before you take the test. Now, they do it backwards. If you test positive for a prescription drug, the MRO (medical review officer) will call and find out if you have a legitimate prescription. So if you should have something in your hair but you don't, that is not going to fail you or look suspicious.

I have never heard of this "toxin wash" before. The methods that I know of to pass a hair drug test do use a stripping method along with a strong cleaner to get to the core of the hair. You are right, most detox shampoos are a rip off but there is one brand that has actually been shown to reduce THC metabolites in the hair.