Oldfarmer knows of which he speaks! (However as a Yank, I have only the vaguest idea of how big a cricket ball is!)

FWIW:

I apologize to Michael Petrov for not seeing his recommendation if Starr's book, earlier. "Great minds", I guess.

General observation:

If I could only have one black powder gun (or, in a pinch one gun, period) it would be a double-barreled muzzle loading shotgun. Properly loaded and choked there is very little that these old-fashioned guns cannot do very well as long as lead projectiled ammunition is used.

Necessary "stuff":

I recommend a nipple wrench; a nipple pick; "good" nipples such as "Hot Shots" (Most "original" or "factory" nipples are junk.); a powder flask and separate powder measure, a shot flask and separate shot measure, a "capper", and a 1/2-inch strait-grained hardwood cleaning/"range" rod with gripping handle ( an appropriate wood ball is fine, as is a wooden tool handle) and a brass gag tip and appropriate jags, brushes, swabs, screws, and worms.

A lace-on recoil pad is not always a bad idea, either. Many of these guns are just a bit short for modern shooters. Newton's Second Law is generally not cancelled for muzzle loading shotguns.

A pair of Gripswell gloves that are designed for double barreled shotguns migh be useful, too, especially if the gun is to be used for range work. Black powder shotgun loads can really heat up barrels.

Loading: Random observations:

Use the best caps you can get. You won't be sorry. FWIW, I have had excellent success with RWS caps.

Powder: "The real soot" is best. Most shooters seem to prefer FFg and it works well. If I can get it, though, I still prefer Fg, heavier charges and (maybe) more "dirt" be damned.

Wads: There are two schools of thought about whether to use filler wads in muzzle loading shotguns. Those who favor the use of filler wads assert that such wads provide needed "cushioning" for the shot (They do not.) and efficient transmission of needed bore lubricant (They do). Nonbelievers (like Starr) assert that extra cushioning is not needed (They are correct.) but can run into trouble with lubricating the bore during continued firing (Hence, old V.M. spitting down loaded bores!). A compromise that has worked for me is to run rubbing alcohol soaked patches up and down the bore between shots, especially if only card wads are used. (Old-time gunfighters often cleaned their guns with "rot gut whiskey". I suspect that rubbling alcohol might be just a bit less toxic!) Otherwise, properly-lubricated felt or fiber filler wads can work just fine.

"Notching wads": Card OP wads can tend to "back out" when they are loaded due to back pressure in the bore. One trick to prevent this is to put a slight "notch" on one side of the wads. If two wads are loaded. make sure that the notches don't "line up" and all is well.

Shot: Use the "good stuff". "Magnum" shot is not only harder than "chilled" shot but it also tends to be more uniform in size and roundness. Besides, with the price of shot being what it is, the extra that one has to pay for magnum shot is piddling.

Loads: While BP can be loaded to practically any common velocity level it does best at about 1000 to no more than 1100 f.p.s., hence the recommendation of "volume-for volume" loading. With cylinder bore guns, a smaller volume of powder relative to that of the shot can contribute to improved patterns. Such loads can perform very well on clays with normal shot sizes. For hunting, it is often recommended that the shooter "come up" a shot size, especially is "shot resistant" game like pheasants is on the program.

Muzzle loading shotguns can be very effective "ball shooters", too. However, this subject can be treated another time.

Cleaning: All the recommendations that have been made have been good ones. I would just like to add, however, that Ballistol can be an excellent product for muzzle loading shotguns. Mixed with water to "black powder strength" it does a very nice job of "tidying up" after hot or cold water cleaning and it also does a very nice job of final cleaning and preservation of leather, wood and metal at full strength.