The thing is Homegrove, there are tons of strategies to get through an all dayer.
Of course, you can never risk getting caught, but most people are so hammered and engrossed in their own conversations (arguments), attempts to chat birds up, play pool, get their hands on some beak, and so on, that they don’t even notice.
The way to ensure such unwanted attention never falls on you is to ensure you show utmost generosity at the most important times, such as buying a mega round, or buying a couple of ‘snack platters’ for the table, which of course helps you soak up the alcohol anyway.
Bottles are a good idea too, and are easily excused away with an aggressive, complaining “The draft’s fucking shit in here, I’m not drinking that shit, this landlord doesn’t clean the pipes properly”. Get on the front foot with that stuff.
Another good one is taking your bottle with you when you go for a piss and emptying some of it down the urinal.