Cleaning afterwards would pretty much require that the crane retention screw be taken out, the crane and cylinder removed and the ejector assembly stripped down. A lot of the fouling will be pushed into the ejector assembly and cylinder arbor so this can't be skipped.
Howdy again
I do not recommend stripping down the ejector assembly of a K frame Smith. Too easy to bend or spring something.
I shoot Black Powder in revolvers all the time, including antique Smith and Wesson Top Break revolvers. The first thing I do before shooting Black Powder in any revolver, antique or modern, is to completely degrease the mechanism with a strong solvent such as lacquer thinner or paint thinner. Then I completely relubricate the mechanism with a Black Powder compatible lube such as Ballistol. I also make sure I have cleaned all Smokeless fouling from the chambers and bore and relubricate them with a light coating of Ballistol.
Of course, I only shoot Black Powder cartridges that have a BP compatible bullet lube such as SPG.
Lastly, when cleaning the revolvers, particularly an antique S&W Top Break, I
do not disassemble the cylinder ejector mechanism. I simply remove the cylinder and work lots of my favorite water based BP solvent through the ejector mechanism. This flushes out all the BP fouling that has worked its way inside.
If I were to go to the trouble to shoot BP in a modern revolver, I would do all those things; disassemble the gun and relubricate with Ballistol, shoot cartridges that have a BP compatible lube, and finally, when it came time to clean I would remove the cylinder crane assembly to clean it, but I would go no further disassembling it.
Frankly, I can't imagine why I would go to all this trouble. Impressing other shooters on the firing line is certainly not a reason to do this.