You tried a lot of things, but I didn't see you mention pulling your skin tightly. My chin requires me to yank the skin as tightly as I can without ripping it off and then move the blade across it with a flat-angled motion. I have to move it a little more quickly than I do on the rest of my face and I swipe it with a slight windshield-wiper motion.

My chin must have a billion tiny little skin folds in it that absolutely must be stretched flat before I can pass a razor over it. If yours is like mine then that's my suggestion

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*disclaimer* I've only been shaving for 3 or 4 weeks, but the process I just described gives me a consistent and much better result. My skin thanks me. Your chin skin & hair may be different