WoWDB

The Dark Iron attack the Brewfest camps at Orgrimmar and Ironforge every half-hour. The quest Chug and Chuck! (H) / (A) teaches the player how to pick up and throw the Brewfest Samplers, but it is not necessary to complete it in order to participate in defending a Brewfest camp. The goal is to protect the three large brew kegs from being destroyed for a certain length of time. As long as at least one keg remains "alive" at the end, players will have successfully defended the camp. (Players do not actually have to participate in the event in order to pick up the quest from the Dark Iron Mole Machine Wreckage in the center of the camp.) The wreckage that provides the quest This One Time, When I Was Drunk... (H) / (A) appears in the middle of the camp and lasts for 15 minutes before despawning.

There are tables scattered around the camp with  Alcohol-Free Brewfest Samplers on them. Pick one up and throw it at the Dark Iron in order to knock them out of the fight. Players do not need to specifically target an enemy; all that is necessary is to be within range (approximately 5 yards, I think) and facing the general direction of the the enemy. Tip: Before throwing the mug, drag it from your inventory to your action bar so you can spam-throw mugs. Brewfest NPCs nearby help out by tossing additional samplers into your inventory.

Be careful about getting too close to one of the dwarves. They will interrupt whatever you are doing and knock you back a fair distance. (Exception to the rule: read next paragraph.) I felt like a ping-pong ball at times.

Occasionally, a large silver mug will spawn on the ground. Run over to them to gain  Drunken Master (buff is applied to one player only and then object despawns).  It causes the player to spin around and fling mugs every which way at Dark Iron dwarves. This will stun the affected dwarves but will not knock them out. Still, it is very useful in defending against large waves of Dark Irons because it gives other defenders additional time to knock them out before they reach the brew kegs. These Super Brew Steins do not stick around for long, so do not try to save them for later; use them as soon as one appears.

Due to the way the event works, it is impossible for a single player or even a few players to successfully defend the Brewfest camp from the Dark Iron. Players best chances to stop the Dark Iron are when their realm is more populated than usual. (This varies from realm to realm, but the first day of the holiday world event is typically well attended because people want to get it out of the way.) So although, as previously mentioned, players do not need to participate in order to interact with the quest-giving cog, it is good form to assist - even low-level characters can help out.

You will know if Brewfest is being attacked and what the outcome is by the emote the Dark Iron Herald yells out.

• Start of attack: No one expects the Dark Iron dwarves!
• Dark Iron win: We did it boys! Now back to the Grim Guzzler and we'll drink to the <number> that were injured!
• Alliance wins: RETREAT!! We've already lost <number> and we can't afford to lose any more!!
• Horde wins: RETREAT!! We've taken a beating and had <number> casualties!
    We can't keep taking these losses! FALL BACK!!

Additional tips:

• If your character's drunkeness is causing your screen to be blurred, run the following command in your chat window to disable the blur effect (without quotes) - "/console ffxGlow 0". To re-enable (I don't know why you'd want to...), just change the 0 to 1, like so - "/console ffxGlow 1".