Tar-like undercoating on 63 Valiant...any way to remove it?

Is started with a old HF oscillating tool and scraper blades. Works well. But i burnt that up and switched to pneumatic mini needle scaler which even better. No chemicals etc and the material lands dry and can swept or shop vacuumed up. But my car was also on a rotisserie. Where a dust mask or other APR for sure.

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