I find it hard playing Samus because of how much footsies is involved in the MU. I typically spam bairs to rid of missiles and to catch Samus attempting to wavedash in to ftilt/dsmash/fsmash. I try to get a read on the Samus' movement when trying to recover, sometimes you can catch them with a bair, and sometimes you can just straight up aeriel their bomb so they don't get the boost. You can bair them a few times and end a string of 3-4 bairs with an up-air at low percents, but combos do not come easy nor do they come often.
When I play Luigi I try to keep in mind that Luigi's aerials come out quickly and shouldn't be underestimated. Well-spaced bairs should interrupt their slipping around (wavedashing). Also, edgeguards are kind of free, but ALWAYS assume they are going to misfire. Getting caught by that is no fun. This is based on my experiences with the Luigis and Samuses in my region