Install "wipe", its in the repos.
To delete dirs use it like this: wipe -rfs
Add a nautilus action (menu system > prefs > nautilus actions) like this to make it available in nautilus (you can then select all the dirs and files you want and shred them with 1 right click):
path : wipe
params: -rfs %M
Edit: you need to install nautilus-actions from the repos for this…