Had to remove a few in my time, used to work for in the Insurance Restoration Industry, wind, water, fire, vandalism, theft etc. For about 4years the majority of my work was front door break-in repair. Got damn good at it and rarely had a call back.
The older Kwik-Set (Schlage had a different style) double keyed deadbolts had two sets of screws, the one-way type described in the post and the standard Phillips. I for the life me could not understand why anyone would install the one-way screws let alone a double key bolt. 99% percent of the repairs I did was done with a size 12 kick to enter and have never seen one taken apart from the inside to get out.
I used a nail set that I had filed down and tapped in the direction of removal to loosen, worked most of the time. They also make it a pain when you need to loosen the deadbolt for adjustment when ever I received a call back..
