Am I eligible for a 72 hour visa and if yes how do I apply for same?

Joe, if you fly from Ireland and then get back again within 72 hours, then you are not qualified. However, if you fly from Ireland to Chengdu, then Hong Kong and then back to Ireland, they you are qualified.

You just need to inform the steward at least 30 minutes before the plane lands at the airport. Then they will inform the inspection bureau in advance. Upon arrival, you just follow the instructions to reach the place where you can apply for the free transit. It's very convenient and easy.