For deletions, the best bet would be to either email support or post on these boards. The correction submission function from your database doesn't really handle deletions... and deletions often require some sort of explanation anyway, so best to do that via email or public board posting.
Generally speaking, go ahead and create the entry in CB and submit.
But, if you are entering something that is complicated for some reason, then posting to the boards can generate some helpful discussion.
Also, if you can't find a fairly common title, it might be best to post on the boards for assistance before you create an entry. Hypothetical example: you can't find the 1970's Peter Parker, the Spectacular Spider-Man series... posting on the boards will result in somebody pointing out that the title is already in the database as Spectacular Spider-Man, The.
Usually the reason behind that occurrence is that the existing cover file is larger than the cover file that you want to upload. The fix is to email the cover to support.
Good rule of thumb: if the thing that needs correcting is complex and/or nuanced, please post on the boards! Even though these boards aren't necessarily a high traffic location on the interwebs, there is a pretty good pool of expertise here (from both HC and from CB users) that things often get sorted out pretty quickly. š