Mineral spirits/paint thinner (not reducer) to soften and remove the sealer OR heat gun on low. A 3M scratch pad (red) or finer helps.

The POR15 epoxy putty works great. I've been using the "J-B Water Weld" as a replacement for the POR15 putty. I have a suspicion it is the same stuff with a slightly different formulation. Not any better but it is available at almost any hardware store.

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“Whatever story you're telling, it will be more interesting if, at the end you add, "and then everything burst into flames.”
― Brian P. Cleary, You Oughta Know By Now