Bit late of a reply, but the simplest way of using dair that I've found is to float above your opponent's head and go from dair to fair at lower percentages, or dair to uair at higher percentages. Shorthopping dair can lead into a lot of other combos (like here https://youtu.be/bJmTMd1lzjU?t=166), but it's more difficult to pull off. Be careful that you don't move too far ahead when setting up dair combos or you will knock your opponent in the wrong direction; not punishable, but ends your combo.Noob question here! What is the optimal use of dair? I throw out that move to pressure or beat some other moves but I rarely get a follow up and sometimes punished for it. It is very important for peach but I dont know to use it effectively and damage isnt that good.. in what situations should I be using it? In what position(oos? While falling? what lv of float?)? In which percentages? What are the follow ups? Ty!
Using dair when falling at higher percentages is generally not worth it as it is simply too risky and unlikely to lead into anything major if the last hit does connect.