brush is the easiest way to get rid of residues, especially from the frame
that’s the moment you run patch with oil through it
Firearm is a tool. If you keep it in good shape and clean properly - no needs to spend money for fancy schmancy bore scope or lights. (Once you see the inside of the barrel after 5K rounds with bore scope you will do nothing else than scrubbing, brushing and polishing it for next two weeks 
)