The welding tip cleaners have the problem of flexing.... this leaves a rounded crown to the bottom of the slot. that will result in a guitar that is impossible to intonate.
When you cut the slot is must slope down and away from the fingerboard leaving a crisp sharp edge at the fingerboard side. That is very hard to do correctly with a piece of wire, which describes the welding tip cleaners quite well.
“Silence in the face of evil is itself evil:
God will not hold us innocent.
Not to speak is to speak. Not to act is to act.”