If there is enough room and enough bolt or nut to grab, I have an 18" pipe wrench that works well. This is usually after a PB Blaster soaking. I recently used a manual impact driver to replace the door latch on my Explorer. It wasn’t rusted, but was tight enough where a simple screwdriver couldn’t loosen the phillips head screws. A power driver would have most likely damaged the screw heads. Used it to tighten the screws again on re-install.