This takes a lot of planning. Know what gate(s) you will be in and contact the MSCs to find out what shops are available. Have the scheduler on standby in case you have a gate change. Do it sooner than later in case certain shops fly off the board.
When I went to France, I made the mistake of waiting until I got to the airport to look for shops. Not a single shop was available. No shops at my departure airport and no shops at my layover airport. I scheduled 4 shops for my return layover. After the movie on the return flight, I read the guidelines for the shops, calculated my cash for the duty free shop, etc., etc. As we approached the airport, gate change with no access to the previous gate. I contact the scheduler. I heard back from him when I was in the air headed home.
"I told myself to quit you; but I don't listen to drunks." -Chris Stapleton