(n.b. They're called soroban here -- mentioned so that folks would be able to look it up more easily.) One is generally exposed to them as a curiosity in math classes, but if you want to get good with them, you go to an after-school cram school. There exist many, even in Ogaki, which specialize in nothing other than abaci. The secret to good abacus use is, again, to drill the "'()#'% out of it.