For those unfamiliar with it, you can see what he's talking about in the first few seconds of
this video and then keep watching to learn more.
Theoretically, since this is safe on shield, there isn't really a wrong time to execute this unless your opponent is throwing out lingering hitbox attacks, or spending most of their neutral airborne. This is Smash, after all, so nothing is guaranteed to work, you gotta earn your windows of opportunity. That dance trotting technique can bait out an unsafe move from your opponent giving you time to glide toss in. Very few characters will actually be hit by a sweetspot uptilt at the end of the string, so I've opted for the F smash and Usmash depending on their weight class when I try it. I also really enjoy stringing a hit of this into a jab lock Up tilt kill, which is also shown at the three minute mark.
Besides throwing it downward for the string, I also jump cancel throw forward on an opponent about to land. Since characters in this game don't want to land with an air dodge, they'll only land with an attack if they feel pressured, but the glide toss lets you close so much distance so quickly, that they don't realize they're in danger until its too late. You can throw forward, the blade pops them up in the air for longer, allowing you to get an easy Usmash or fsmash, or maybe keep walking to land your sweetspotted uptilt. There's a ton of freedom here.
I encourage you to keep practicing glide tossing and trying it on different opponents.