Factory undercoating removal

I need to remove the factory undercoating on my car (73 Duster) & was wondering what a good/better way to do it is? Heat gun & scraper? Chemical to soften it for scraping off? Wire wheel/brush? I did this years ago on a 63 330 wagon I had & was a very long & tedious job scraping it off. Now I must do it 30 years layer & on the ground. (No access to a lift) I know it's a long messy job, but time is not a concern, just wanted to see if anyone here found a more efficient way of doing it. Also, can someone recommend a GOOD undercoating to replace what I remove, that is as good as the factory stuff? Thanks all.