You need a flat head screw driver that fits the slot exactly. If there is any play it will chew the head of the screw, than you are ******.
Once unscrewed it is still difficult to get out of the hole. I tried everything such as long nosed pliers, tweesers. In the end, a length of thin fuse wire was what I used to drag it out.
Stay with it though the improvment on my bike was awesome.