removing undercoating

The only undercoating I have ever removed was when I re-did my '68 GTX in 1981. It was in the dead of winter on LI when I did that part of the job in the wheelwells. I mostly used a flexible putty knife with a hammer. The undercoating mostly just chipped off.

Now that I am working on my '68 'Cuda in Texas, there is no hope of having that freezing weather way down here. I will have to resort to the heat gun, which I recently purchased el-cheapo at Harbor Freight tools for around $8 on sale.