I was injured at work several years ago.
At the time of the accident I was a daily smoker and had used cocaine approximately 2 weeks prior to the accident. Due to my injuries I was unable to work. I had been out about 2 weeks when got a call from the HR department requesting that I needed to be drug tested. They were sending paperwork VIA FedEx. When the paperwork arrived I quickly found out that they wanted me to have an hair follicle test. I did some research and found a system to beat the test close to the one you described.
I got the ingredients and followed the directions as I had read them . The next day I drove to the testing facility and had the test . All this happened because the company was looking for a way to relieve themselves of any financial responsibility regarding my injuries. 72 hours later I got the results back and the results were surprising all drugs they were testing for came back with negative results. Now I don't know if it was a fluke or if the procedure I followed removed or masked the contaminants they were looking for. That has been my only experience regarding hair follicle testing.