Ayyyy let's talk about running grabs.
So whether or not it's jump-cancelled, a running grab often pushes Nana too far away for her forward/down tilts to connect for a fast wobble on certain characters. This means that if the opponent is at low%, they can easily mash out before Nana's forward/down tilts start connecting and the wobble truly begins. We know that from a standing grab we can typically get a wobble off of a grab even at 0%, so not converting off of these running grabs really really stinks.
I mentioned a while back that a remedy for this is aerials. Some other suggestions were Uptilt and Jab. Jab was nice because the back-swing goes so far that it will often hit, but Jab-wobbling is weird and difficult. Uptilt works to true combo into the regular F-tilt wobble. It's also nice to Uptilt because even if the opponent escapes, catching them with an Uptilt can sometimes be converted off of.
But anyways, aerials. Nair and Dair both reach far enough behind them that you should, in theory, be able to use them to convert into a wobble. The aerial needs to be L-canceled, but this is actually relatively easy to do. The idea is to L-cancel with Z; this Z input will also activate the next pummel. Fantastic!
So the inputs go something like this
grab (Jump cancelled)
Pummel
Jump+A (you have to do this before Popo is actionable, otherwise the A will input an early pummel)
Z (L-cancels the Nair, innitiates a Pummel with Popo)
Tilt control stick + A (tilt with Nana)
Notes:
The Nair has to be performed pretty quickly after leaving the ground, obviously being frame perfect would be nice, but not at all necessary. Just don't go for a landing Nair or something silly like that.
The tilt is just like the tilt for starting a normal wobble, and it brings all of the problems. Don't charge an F-smash, don't do a dash attack, don't jab, etc.
If the grab isn't jumpcancelled, you have to wait 10 frames since Nana is chilling for another 10 frames.
Anyhow, it doesn't take very long to learn, here's a gfy visualization.
Here's a link in case the gfy doesn't load:
http://gfycat.com/PoliticalRawDiamondbackrattlesnake
Once that first pummel connects it's all over, as true a wobble should be.
This thing is also pretty stylish, so if you want to learn it for that purpose I'd say it's worth it. You could even wobble with only aerials if you wanted to, or something like Pummel -> F-tilt -> Pummel -> Dair -> Pummel -> D-tilt -> Pummel -> Nair -> etc. would be super cool.
EDIT: Reverse F-tilt works, along with the jab and Uptilt, to maintain a wobble.