Whats the best way to remove under coating?

[lonely king]

Can anbody please tell me what the best way to remove undercoating?the undercoating is in the trunk of my shoebox,seems like a older restoration job from a while ago.It has surface rust as i removed it by scrapping it .but those are the parts that are cracked.There are some spots where is still nice and tar like.these are the spots i need help with..Any advice will help guys,,

[Tha Driver]

I'm told dry ice will make it break right out. Heat is the other method (propane torch or heat gun), but it's really messy.
~ Paul
aka "Tha Driver"

I checked today and... this is the oldest I've ever been.

[lonely king]

hey guys sorry for posting in the wrong forum..

[lonely king]

thanks driver ill try that..