a bronze bore brush is good to have, and dont forget a nipple wrench, & its good to have a couple of spare nipples, a capping tool is handy though not necessary.
when you start cutting your own patches, patch lube of some sort, either commercial or many make they're own.
i like a 28 guage shotgun swab on a sg rod for cleaning, it fits the bore tightly and really scrubs well. i also keep some pipe cleaners and q tips for cleaning the hard to get to areas, and i use rubbing alcohol as my last swab down the barrel to help absorb moisture from water cleaning, on the q tips for getting into tight areas, and to soak my nipple in while cleaning the rifle.
a couple of small funnels are handy, i first cap off my nipple and fill the bbl with warm soapy water and let it sit 10 minutes or so to loosen fowling, then a short piece of clear plastic tube 3 feet or so long, that fits snugly on the nipple allows you to use a gallon jug of soap/water for cleaning, just drop the tube in your water container and pump your cleaning rod up and down the bore & hydraulic action sucks the cleaning fluid into and out of the bbl well.
Lastly its always a good idea to wear shooting glasses and hearing protection, same as any other firearms.
Keep a notebook of some kind to record load combinations and accuracy results, it can be as simple or complex as you want it to be, but at the minimum, powder type & charge, ball diameter and patch thickness, & group size & range distance.
this makes it easy to eliminate obviously bad load combinations and further pursue the ones that show promise. I also mark this onformation on targets, at least the promising loads, and store them in a loose leaf notebook along with my notes. easy to refer to and the visual aid tells me more than just a note about XXX sized group.