One tip that has really helped me a lot is most International duty free shops will let to pre-order online weeks in advance, often from a larger selection than they keep on-hand in the shop. Some shops you pay upfront, some you don’t pay until you pickup. Usually when you pay later, you can pick and choose which bottles you want to buy and which to put back on the shelf. The real beauty of pre-ordering is you just walk-up to the customer service desk, they already have your bottles ready, and then you just carry them on the plane since it’s after security checks. Also you’ll know what they have at the airport and what prices are, so if you find something better or cheaper in town before you get the airport you know to buy it then.