Nice project, doing something very similar on my mk3.

Bit of advice you might want to try.

With the sound deadening (bitumen) I was using a hot air gun. Found this just made it soft and more likely to smug across the panel.

I found pouring boiling water on it made it blister off mega easy.

Then leave to dry and a bit of wire wool and white sprits for the left overs

Obviously have some newspaper or towels to mop up quick.