Black Powder is an excellent set of rules but hardly skirmish rules. If you want to play Black Powder there are two things I strongly suggest: 6mm or 10mm scale and a large table.
For 28mm skirmish games set in the Napoleonic era of course Sharp Practice by Too Fat Lardies comes to mind. It's made for proper skirmishes of up to 100 figures a side, each model depicting one man. Very fun set of rules indeed, as in my experience all the Lardies games are. There's no such nonsense as points values or such but you don't really need that kind of stuff. The game is based on the ability of leader figures, called Big Men in the context of the game. The game uses blinds and random unit activation by the use of cards. The main thing about Lardies games is to keep in mind that the rules aren't complicated, they just don't use the all too widely accepted d&d/GW-style mechanics so they require a little getting into but it's worth it.
For even smaller level engagements there's Ganesha Games' Song of Drums and Shakos (based of course on their Song of Blades and Heroes mechanics). I never played SoDS myself, only a variant on SoBH and it plays excellently. Mostly done for small warbands but fast and elegant.
Napoleonic skirmishing is a bit underrepresented when it comes to rules sets, especially compared to the number of Napoleonic battle rules sets. But as always in wargaming, if the period exists somebody made miniatures for it and somebody wrote a rules set about it if only to be able to get into a fight with the other guy who wrote another rules set about it.
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