take the interview, if you fail the test regardless of what you do, well too bad. now, this is what i did. i took one a couple of years ago and before that i was a regular smoker (i.e. everyday smoker), but stopped for about a month and a couple of weeks at the most. for mine, i had to go to a lab so that helped me pushed it a bit... i trimmed my hair, but not that much, like #6 in one of those machines, still they could use hair from your arm pits or wherever. i shampooed my hair a couple of times every day, exercised and drank a bunch a bunch of water, none of which i read helped for a hair test, but the shampoo part. the morning before the test, i took a shampoo (kit of three), that contained some weird ass looking green aloe type of thing and i passed. think about the testing methodology. you have to have more than a X% to be determined to be using drugs (statistically significant??) so i guess the 3 month you are supposed to be clean were too much for me, or the shampoos did work. do not know. best of luck, and take the interview, and then worry about not passing. do not tell them a story; that does not sound very bright. if they cannot take you cause you do not pass, fine, but don't tell them you went to a ziggy marley concert and people around you were puffing...later...