Must have - cannot remove fouling, powder, plastic/lead, without it.

I do use a brush in my 12 bores. I do not use a brush in my 20 bore Flintlock. The 20 bore, sees only water for solvent and after it's dried, WD40 to finish.

The gun he was demonstrating on, was already clean, so I guess, no need for solvent - or the brush.