I've got a special screwdriver designed just for this purpose somewhere. It has a cylinder shaped piece over the slotted part that holds it on the adjusting screw so it doesn't slip off. It is on the end of a flexible shaft (kinda like a speedometer cable) with a nob on the other end. I'll try to find it an post pictures. A "Google" search may yield the same thing quicker.
EDIT : Try this :
https://www.amazon.com/OEMTOOLS-2506...1484361&sr=8-5.