The shorter barrel Blackhawk in .357 is a poor choice to learn "twirling". The tall front sight and the adjustable rear sight have some nice sharp edges, and they are going to bite. And you are going to drop it, probably often.
I recommend you get one of the metal "non-guns" (metal for the weight) and practice twirling with that, to develop a level of skill, before going to a real gun for showy "stage moves".
I think the Blackhawk is the best SA to use, I own several. But if you're wanting the "authentic" old west look, the Blackhawk is the wrong gun.
A "New Vaquero" is Colt size and Colt shape and is, (or was) available in .357 as well as the traditional .45 Colt.
Can't help with holsters, mine are Hunter (leather, not a cowboy rig) or Uncle Mike's nylon, and are for carry not fast draw games.