In full agreement with the above.

Couple of small points to add:
Make up a gallon of 'Ed's Red' and slosh the stuff through the bore. It loosens lead as well as any solvent known, and because of the minimal cost there is no need to be thrifty on solvent.

The wet-strength kitchen paper or paper-towel ('Viva' brand in Australia) completely replaced flannel or 'four-by-two' for all my bore-cleaning tasks many years ago, including shotgun, NE doubles, bolt-rifles etc. Again, minimal cost so I use heaps and end up with a better job.

The best lead-remover for shotguns IMHO is the stainless-wire loop-brush (for want of a better name!). Those things are just amazing! As a kid, I scrubbed leaded shotgun bores for hours with bronze brushes to remove lead: no more! This photo shows the first single pass after shooting a dozen of those mongrel useless RC4 slugs!