Like many of the holidays, Brewfest is one of those holidays where you need to start relatively early and miss few days in order to get all the achievements possible, and get the meta-achievement. I generally stay away from these types of holidays in Wow, but this one really don't seem too horrible, so for some reason, I'm trying it. But then you do the math, and it's really not that hard. Here's the breakdown:
For those that may be reading this a couple days late, you'll most likely have to start no later than September 29th. That will get you to 350 Tokens. You'll need 350 for the outfit so you can complete Disturbing the Peace. As Brajana points out, if you save up and buy all 3 clothes pieces (350 tokens), you can return them for full value in 2 hours.
This schedule assumes that you do all of the dailies each day. You'll get 40 tokens the first time you kill Coren, 40 when you take out all the pink elephants, 10 when you do the first brew delivery quest, and 10 when you throw beer at S.T.O.U.T. Other than that, you have the daily to ride through IF or Org to bark the beer (15 tokens) and the daily that occurs every 1/2 hour to get the Dark Iron Dwarves drunk (10 tokens). Then finally, this assumes that you can deliver the kegs of beer 15 times in 4 minutes (2 tokens for each delivery).
So... 55 tokens per day, with the first day netting an additional 100 from quests. At 5 days, you'll have 375.
If you want to walk away with Hops and/or the pets, you may have to spend a few more days gathering tokens. But strictly speaking on achievements, that is what you'll need. Remember, this is based on being able to do the keg run 15 times in 4 minutes. If your lag means that's just not possible for you, you may need to figure out other math. But even if you only do it 13 times, you can still get the 350 in 5 days.
Edit: Had inadvertently missed the Elephant quest which gives you 40 tokens. I updated the remaining numbers and pushed back the Due Date accordingly.