CO use Terminal 2. Just be mindful if you have to transfer to Terminal 3 that you can no longer make the journey on foot via the glass aerial walkway. Access from Terminal 1 to Terminal 3 is blocked off for some reason (anyone know why?)
You now use the aerial walkway to the railway station and then go down to street level where there is a free bus service to Terminal 3 - It runs every 8 minutes during the day.
I made this transfer last Friday afternoon, including immigration, baggage delivery and check-in at T3 in 40 minutes but I would admit that it was one of those occassions where everything seemed to go exceptionally well.