Drug test tomorrow - Advice wanted

Ok folks, i'm far from new to the drug testing and on the spot notification. I've used various drinks in the past - all masking agents, not used to flush the system. They have always worked for me. I'm 6'2 170 pds, very high metabolism and not much fat. I've always drank a lot of water a few hours prior to the testing and peed frequently before taking the test.

Now, it's been some time sine I took a urine test - which was sent to the Lab. I was in the Military and it came back clean. I had smoked the night before and was a frequent user. I had used carbo-clean or Q-carb, can't remember which and drank probably 1-2 gallons of water the day of the test along with the drink.

Anyway, tomorrow I go in for a drug test for a job. I'm sure it's Urine based - and probably a lab test.

I don't have time to order any substitutions so don't bother telling me about them. I'm aware of them anyway.

My question to you guys is this. Should I just go buy a test kit sample and test myself tonight after drinking alot of water? It's been only 1 days since I last smoked - so it would have been 2 days roughly by the time I take the test tomorrow. I've only smoked 2 times in the past 1-2 months. And only about a total of half a joint between the two.

I was thinking of just drinking about a gallon to 2 tomorrow before the test and pissing several times before hand.

Should I bother with a masking drink from GNC? I have used them 3 times so far, each time a different brand - but I had also drank a ton of water along with the drinks each time.

So basically my question is this. Should I get a drink or just go pure dillution with the water?