It won't train the Betta, Bettas are either aggressive or not. Throwing other fish in for potential slaughter (either the other fish or the Betta, Bettas more often than not end up as victims not killers) is pointless.
All these questions sound like you're planning on fighting these fish for "fun" which is frowned upon. The only place you can get true fighting plakats is Thailand/Malaysia, Bettas in the west are the equivalent of poodles.