Yes blood tests are easier to beat because the detection window is short.

One of the best shampoos you can buy to strip your hair is from Zydot. It is available online from many sites in the U.S. but it looks like you are in Denmark if I remember correctly ( I can't see your flag while typing this). You should also go to the quest diagnostic website as they have FAQ's on hair testing and a little show and tell on how they do it. You can't shave your head as like Birdgirl said you can be rejected for insuffcient sample or they can use other hair. If you stopped smoking now your body will still be pushing dirty hair out from underneath the skin. You need to keep your hair and treat it. Other things you can do is bleach it then add the hair color back, UV exposure, swimming in chlorinated water, or a hair relaxer.

Ok it was Sweden.