When servicing drop targets, sometimes you have to reinstall screws where
access in only through the wiring harness. Even my expanding top
screwdriver wouldn't hold the screw head as I directed it towards the hole.
This tip was born out of the desperation of dropping the same screw 6+
My tip is to use a candle and hot-wax to bond the hex-head screw to a nut
driver. The wax (or hot glue, if you must) will allow you to fish the screw
through the maze of wires and bracket and get it started in the hole. Once
screwed tight, the wax/glue will release easily.