I'm about to try and remove mine . Would it be better to use heat first ?
If you are embarking on a restoration and paint condition does not matter, I would first apply heat as it tends to break the rust bond allowing penetrating oil to get into the hinge pin. I have had most success by getting the hinge a dull red/orange color. Be careful to not get too much heat to the sheet metal laminated portion as there is a risk of melting or deforming it if not careful. It may take several cycles of heat/oil/beating to get the pin to start moving. Be patient.
When reinstalling, I like to use a liberal amount of antisieze on the pin.