Once you have cleared Dublin Airport security, the US Preclearance screens will direct you when to go to US Preclearance. Passengers should not present to US Preclearance before their flight opens. Please see example below.
We recommend passengers to arrive at the airport 3 hours before their scheduled US flight to allow enough time to pass through Dublin Airport Security and US Preclearance.
If you are travelling from Dublin to the US on your connecting flight you can use the Preclearance facility in Dublin and will not have to go through US customs when you land.
If you fly from Dublin to another airport outside of the US then you will not use US Preclearance
Yes, the 51st&Green US Preclearance Lounge.