I use a Multi Function tool from Harbor Freight. It is a sonic vibrator and the knife blade takes off undercoating easily. It has many adapters, saws, sanders,etc.

1954 Chevy Half-Ton
In the Stovebolt Gallery
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1958 Chevy 1/2-Ton Stepside
In the Stovebolt Gallery
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"Time's fun when you're having flies." ~~ OLD FROG