I don't use dsmash since a fresh dsmash breaks the opponent out of the grab. Dtilt never has that issue. Against characters whom the dthrow CG lasts a while on, though, I think it's typically best to just not have Nana do anything and also not pummel with Popo. That way, the dthrow CG lasts longer, both due to fewer other things racking up damage and dthrow occupying more of the stale move queue. The reason that is nice is that if the opponent doesn't DI away and isn't at a really low percentage, you have an easy wobble set-up, but if they DI away too many times, they'll be close to an edge, which leads to a handoff, which itself can directly lead to a kill or a wobble. If the opponent decides to DI away until they're at a percentage where they can escape with a double jump, and then DI up and in and jump to escape when they reach that percentage, then doing damage more rapidly during the CG decreases the horizontal distance the enemy needs to travel before having this option, meaning they'll less often need to worry about getting near an edge.
That all said, I'm pretty sure this guy is talking about dthrow -> dair since he mentioned having Nana short hop, which, as others noted, is easy to escape.
