Falco's dash attack into upsmash is kind of hard. You do not need a down throw to do it, but I find it easier that way. You want to hit with the beginning of the dash attack then do an upsmash as quick as you can. The dash attack should stop and the upsmash should come out instantly. Falco's boost smash is kind of the samething thing except you have to to charge the upsmash so he can slide.