I have a drill driver with out "hammer" and it still works much better than a screwdriver.
1. CLEAN the heads first, with a small pick. A clean head makes all the difference. PB around the screw.
2. Take a flat punch the size of the screw head and and smack it once or twice with a small hammer. This will shock the screw and flatten down the head if it has been camed out.
3. driver set to high torque, make sure the bit is seated, lean into it and use full power.
I never broke off a head. had 2 that were so bad I had to drill, and 2 the driver couldn't reach. Loosened them with a small chisel and vice grips.
