All different types of Pokemon are swarm Pokemon. You have to check the Pokegear's radio on Professor Oak's talk show to find out which Pokemon it is that day. Generally, rare Pokemon that can only be caught in swarms or very little at normal times appear in swarms.
Swarming on Route 1.
There aren't swarming pokemon in pokemon black.
yes in Route 19Rarity:SwarmTo get Clamperl you need to listen to Prof. Oak's radio show and they will announce a Pokemon that is swarming around a route you just need to wait until they say Clamperl is swarming around Route 19.
Baltoy can be found on Route 3 if they are swarming there. To check what Pokemon is currently swarming, listen to Professor Oak's Pokemon Talk, he will say what Pokemon is swarming where.
A Pokemon Swarm is basically a Pokemon that is swarming in a certain area say a bledum is swarming the beldum has a higher apperance rate
swarming Pokemon are Pokemon that appear daily on a certain route. you have to have obtained the national dex first though on the games that they appear on.
Chances are that the Pokemon that is swarming is not available normally in the Sinnoh region.
In front of Fuego Ironworks, but only when swarming.
there is no way to do that
it's random
no you can trade soulsilver pokemon to black
he is not in Pokemon soulsilver or Pokemon heartgold