Wow next time I go to Home Depot I'm going to buy some really sketchy things just so I can do this. I don't know about your local stores but mine has a seperate section of funnels right next to the tubing along with valves and clamps, It's basically a beer bong section(it's great).

The best way to buy supplies if your buying alot of things all at once is to bring a freind or grow partner and split the list so that everything wont look so obvious. But like some of you have said before, WHO REALLY GIVES A FUCK!!! out and happy growing.