Heating the screw softens the wood fibers around the screw and also breaks any glue bond. It causes the pores of the wood to open up and the wood to swell slightly.
Remove old paint around the screw and in the screwdriver slot.
Add a rust penetrating oil like PB Blaster
I used a hacksaw (or sawzall) to cut a notch in the top to created a slotted head which would take a conventional flat screwdriver, when the phillips head was slipping.
Get a metal drill bit the size of the screw head, put your drill on the low speed/high torque setting and drill the screw out.
I don't know of anyone who has got an Ez Out to work.