Please don't promote this shit on here. First of all there are much cheaper ways of sneaking in booze than buying a $5 bottle cap, and second people need figure this shit out for themselves. The more you post your secrets online, the more likely you will be found out when entering the festival.
I am sure it is somewhere here. (Seems I recall seeing it last year.) But drinking, though fun, can be a killer at these things. Limited sleep. Hot sun. Exposure. Dancing. Sometimes nominal food. - All this taxes the body. Add on to this a few shots of vodka at the wrong time and you are toast. There are always those people passed out cold at 3pm on the hill getting fried in the sun and missing great shows. Have your fun, but you don't really want to pay $330 for a ticket to be passed out while the Presets play. And just because you can drink a pint of whiskey on Friday night at home, don't think you can do the same Saturday afternoon at the Gorge. People end up missing whole days due to underestimating the impact of substances (alcohol and others). It is a long four days. Enjoy them all.
(But seriously, a good shot or two of Islay Scotch added to Kokanee really hits the spot!)