Choice Transfers are a shuttle service operating between both terminals, and to and from the bus station, plus to places further afield. Their phone numbers are 00 359 878 785 665 and 00 359 887 785 665, and they speak English. They were very helpful when I phoned them. They have a desk in Terminal 1 opposite the exit door from the baggage claim area. Also they have a website, firstname.lastname@example.org
Hope this helps.