1. The consulate (a freezing portacabin seperate from the main embassy building) opens between around 9-13:00 on Monday, Wednesday and Friday. I would advise arriving early - I got there at 9.25, they were already open and a few people there, but I was able to hand over my documents for processing straight away. By 10am the place was really busy and there was a long queue.
2. It takes about 2-2.5 hrs for the processing, you can leave and return to pick up, or sit and wait (bring warm clothes!)
3. If you are coming from the airport you can get the Aircoach which goes to Greystones. This bus goes up the road the emabssy is on and drops you a few minutes walk away (Mount Merrion stop). The bus driver tells you where to get off the bus and this costs 8E, compared to 40E for a taxi. It only leaves hourly (on the half hour), so if you just miss the 8.30 bus you might take a taxi to get there in good time.
4. You need an Irish postal order to pay the fee (150E for UK citizens). I got mine in advance, but there is a post office close by which they will direct you to (the only currency is postal orders in Iranian embassies world wide!). It costs an extra 3.70E for the postal order fee .
5. You also need to fill in the form from the website and take 2 passport photos (in hijab ladies) and your passport. No fingerprints or interview (for me anyway!).
6. They say it is possible to apply by post if you have the time and also the Irish postal order/Irish stamped return envelope. So you would need friends in Ireland to send you these first.
7. It was easy, the staff are friendly and there was plenty of chat to be had in the waiting room - mainly in Farsi of course ! Good luck!