Interestingly enough, I had this same question a while back, except for Ness. I wanted to be able to djc nair out of shield or a dash for quick pressure (or do flashy combos like djc fair djc nair djc fair again). I tried using C-Stick for attack but never really got the hang of it. Instead I just ground out this button combo—

->

->

+
—basically doing it very quickly in order to let the Control Stick return to neutral before I hit A. Not gonna lie, it was an exercise in teeth-gnashing frustration for the first few practice sessions. But nowadays I can to it pretty much every time, and I'm glad I learned. Fade-back fairs are a really valuable ability for Lucas to apply safe pressure. Also, I think the benefit of using tap jump for the second jump is that you have that small degree of aerial control when you can tap up, up-left, or up-right in order to do fadeing back/advancing djc nairs. It's really reassuring to have that level of control over the spacing.
@
Xcite
I didn't know DJC nair could be used like that! I'd always wondered about the practical applications of avoiding the strong hitbox, but I'd never really bothered to try it out. I'm gonna need to give that a shot!