Pre employement screen in 7 days

Hello all,
Iam 26 yrs old, weight around 190 pounds and 5"10 tall.
I was a pretty regular smoker, but now mainly a small bowl or two a day if that.
I exercise alot and drink lots of water and I am in pretty good pysical shape.

However I have a pre employement screen in a week.

I have been reading alot about dilution and b-12 to make my pee yellow.
I also bough a home drug screen kit to do a test run a day before my offiall screen to see if dilution works.
Does anyone have any other suggestions? should i go to GNC and pick up a drink to help me out