Scum Dumb

A person who is scum and who believes themselves to be scum smart, but in reality they are so stupid they would try and claim for disability benefit and home help from someone they work out with at the Gym

They are definitely scum dumb as they tried to make an insurance claim for new carpet claiming it was damaged by Penguin that flew in through the window

Scum smart

A person who is already identified as scum, but has an uncanny ability to retain knowledge relevant to criminal activities such as claiming benefits fraudulently and convince others they are right and justified to have them

You have to be scum smart to live in the slums and still afford a Mercedes and designer gear.