The ONLY way to beat the test as a daily user is to drink LOTS of water a couple of hours before the the test and pee several times before you give your sample. A very dilute sample MAY not register any THC, but the chances are that you will come up positive regardless of what you do. We all know that THC is fat-soluble, and that is why it take 2-3 weeks to leech out of your fat cells. Drinking a lot of coffee along with the water will help, caffeine is a diuretic, and will help you pee more to dilute your urine a little quicker. Don't waste your money on anything that claims to "flush your system", they are all bullshit.
BTW, I'm a Lab Tech, anf have run the GC-mass Spec analyzers that they will be testing your urine on for ten years. You can't fool them, all you can do is make your urine as close to water as your kidneys can get it, and you do that by drinking water, LOTS of water (a gallon over the course of a couple of hours before the test). You may get the shits after drinking that much water, but it's not serious. It's like when you oferwater your plants, the extra comes out the drain holes (which in this case is your ass!!!)
Good luck, and drink up!