Summarize this article:

Keep the gloves on at all times to protect your hands. They will protect you in case any of the tools slip when in use. Also, put on polycarbonate protective glasses or goggles to shield your eyes from metal fragments. Rotary tools have detachable heads. You can swap out the heads with 1 of many different accessories. For cutting screws, you want a flat wheel designed to cut through metal. Fit it onto the rotary tool according to the manufacturer's instructions. Test the wheel by turning on the rotary tool. The wheel should spin freely at a consistent speed. Keep your biggest flat blade screwdriver nearby to use as a point of comparison. Tip the rotary tool so the edge of the wheel is over the screw head. Lower the tool down to begin cutting into the screw. Work slowly and carefully to widen the cut to the size you need. An ideal slot creates a tight fit for the screwdriver so you can turn the screw with maximum force. Push the screwdriver head into the slot you made. Continue pushing down on the screw as you begin turning it counterclockwise. If the slot is effective, the screw will loosen and pop out.  If the slot is too small, you can widen it with the rotary tool. If the slot is too big, you may not be able to remove the screw this way unless you can find a larger screwdriver. Some screws will still be rusted in place even after you cut a perfect slot. Use heat to remove them.

Summary:
Wear heavy leather gloves and protective goggles. Place a cutting wheel on a rotary tool. Cut a slot the size of your largest screwdriver into the screw head. Use the screwdriver to remove the screw.