Cleaning a window seal

I started with a plastic tent stake. It had a T shape or profile and a short arrow like point. I whittled the point to a long slow taper. This became a fluted tool to dig out the heavy stuff. A second smaller plastic tool was used to get even more stuff out of the square inside corners. Lots and lots of old rags. I tried mineral spirits and a couple other solvents I had on hand. Nothing worked better than charcoal starter fluid. I don't know why or what's different about it. Once the gasket would no longer leave black on a white tee shirt material household cleaner removed any oily residue that may have been left by the lighter fluid.
I have spent as much as 8 hours, spread over a few days, refurbishing one 68 notch rear window gasket.