Falcon has a few ways of doing it depending on the type of dash. Foxtrotting (in the video above) lets you reset the dash rapidly-- and you can input another move once he comes to a stop as well. If you don't hold forward after that first lunge, Falcon won't have a cooldown slide.
However, if you are talking about doing it out of a full dash, you'll want to press backwards during the dash so Falcon will turn around, then input whatever you want. It significantly reduces the cooldown lag from the dash and you can do a reverse forward smash from it (stutterstep fsmash), which has more range than a normal forward smash since Falcon moves forward with it.
Personally though, I would recommend pulling up a shield to stop your momentum, then do something (if you're doing it out of a full dash), simply because it's more convenient and will have about the same amount of cooldown time (or less, haven't tested frame data for it) than the already reduced cooldown from turning around during the dash.
If you want to get fancy with dash shenanigans, you can always get Falcon into the running animation, press backwards -> neutral as he's turning around, then press the control stick back in the direction you were dashing toward. Falcon will turn around like he's going to run in the opposite direction, then his animation will jump back to dashing the way he was originally going. Silly for getting dash grabs too (or going into a foxtrot up close!).