I wish to delete a user which I know how to do but what I don't know how to go about doing properly (system-wide) is deleting there files and driectories owned by them so it was like they never existed as this user is gonna be just a test and so I don't want the clutter it's gonna create while I test with this user. Any tips are helpful along with scripts are welcome.

How about ?

Got it guys thanks I deleted the user along with home directory where slackware doesn't support deluser i did userdel to delte user and there home directory did find / -user 666 (userid) -print | less to go through all the files that were created during testing (had to use userid since user no longer exist it associates files with that users id not name anymore so the name can belong to a whole nother person without alloowing them access to files that aren't theres) and I removed all files owned by them (which was nothing system related specificially so it was all safe to remove