Vice grips are great for the easy extraction but my favourite is the fine blade high speed cutter cutting the slot for a flat blade screwdriver like Bear said.
Another is drill out as much of the broken fastener and use a tap to remove the remaining thread.
Heat gun on HOT is very useful but above all, patience.
I've done this quite a few times by gently heating the adjustment knob with a heat gun and pulling straight off. Install is just pushing straight back on, hope that helps.
Broken Bolt Extraction
in 6 Cylinder Tech
Posted
Vice grips are great for the easy extraction but my favourite is the fine blade high speed cutter cutting the slot for a flat blade screwdriver like Bear said.
Another is drill out as much of the broken fastener and use a tap to remove the remaining thread.
Heat gun on HOT is very useful but above all, patience.