How to >>COMPLETELY<< remove an application?

[Richard Owlett <rowlett@cloud85.net>]

I recently installed grml-debootstrap from a purchased DVD set of 
Jessie(8.6.0). I have minimal available bandwidth so I install strictly 
from DVDs.

I have discovered a potential bug for my specific use case and believe 
I've narrowed the problem source to two specific files.

I have used script to record some of my test runs after I had edited the 
files in question.

I wanted to record a test run duplicating the as originally installed 
environment. I used Synaptic to remove the package - choosing the "Mark 
for complete removal" option. It notified me that it would remove 
configuration files which was why I chose that option.

I reinstalled grml-debootstrap from the same DVD set. I did a dry run 
and got a quite different set of errors.

IIRC I've seen discussions about removing EVERYTHING related to a 
package. I don't recall the details.

What is the most effective way to completely remove an application?

If all else fails, I can reinstall Debian completely to a new partition. 
But I'd like to use this as an "educational" experience.

TIA