If you are going to blank the media use the security erase command to the
drive. That is what it is there for.
In the case that you want to blank the entire media these options are indeed available. My original question was to leave the system intact but to remove certain files from the user area, such as gpg key files for example. The idea being to have the user area set up with the original desktop but simply switch the username to the new owner but leave the computer in a state where there was no easily accessible trace of any sensitive files. So in this case blanking the media is not what was intended.
If starting with a clean install was the aim then any of the secure blanking options for the entire disk (or partition) would be admirable solutions.
Thanks for the suggestions though - and in this case it looks like shred is a good enough option for my situation.
