When you buy your booze, get it at the airport and tell them you will be in transit and they will put in a special sealed bag for you.
When you land at Istanbul you will do your customs checks there and if you are on a quick connection you will simply leave this terminal and use the interior walkway to domestic terminal.
You are allowed to buy one bottle of spirits here then go though the scanners again for your internal flight to
DalamanWhen you land you enter the domestic terminal but getting down the stairs you are greeted by an official who will put you on a bus to collect your luggage at the International terminal where you can buy further duty free
Your passport has already been scanned at the duty free in Istanbul so they will not sell you spirits if you have already got them there
For people who are staying in Istanbul a few days, I am not sertain about bringing that sealed bag back into the terminal and would not chance it so put it in your hold luggage