Everyone seems to have a different solution to this challenge. Here is what I did.....
After I went back and forth to hardware stores and other stores I thought could help, I finally smartened up. I took everything.. everywhere I went. In this project first I found that you need to get your false bottom or whatever way you plan to use first. Then you take this to the place you are buying a cooler from to check if it will fit. I first bought a Phils false bottom and it did not fit in the igloo cooler I bought. I also had a ton of problems with fitting something in the spigot. Thinking it would solve my problems I drilled the hole just a tad bigger which was not a good thing to do. The real solution to this problem was when I went to a LHBS (not all that local, but a drive), they had a Kewler Kit. By then I had scraped the Igloo cooler and bought a rubber maid one that the Phil's bottom fit perfectly in, but when I tried to put everything together the space between the fittings inside the cooler was not wide enough. It just so happened that the stainless steel false bottom worked like a charm so I got the stainless steel false bottom. That is where I am now. It workes. Stainless steel false bottom, Kewler kit with a Rubber Maid 5 gal cooler. It leaked a little (not from the cooler, but from other fittings) so I followed Dude's advice and got Teflon tape. Wow... stuff is great and works like a charm!
The problem I had when I used it was I used regular vynle tubbing to connect the inside fittins with and it softened up and came loose. I now have high temp tubbing and stainless steel clamps to just be absolutly sure.
Like I said before. You will be brewing in 10 minutes!... if you have the right stuff....