A readback is exactly that - you are reading back what you have written on your kneeboard.
But you aren't trying to write as the controller is saying it, because he has been saying more or less the same information to all the other aircraft on the field. What you have been doing is listening to him and writing it down BEFORE making the call. So when he comes up with 'EI-XXX, runway xx, wind yy qnh 1234', you are just checking what you have written previously. And thats what you read back.
Try making up some aide-memoires for standard calls & clipping them to your kneeboard - it worked for me.