I tested this again
Here is some reading for people who are interested. (You should be interested)
Go into training mode, put it to 1/4th speed, use marth as an opponent.
Dthrow, now as soon as ddd can dash forward immediately press Z.
when i say as soon, you have to be frame perfect, just keep mashing forward until you see ddd move (its in slow motion).
The normal dash grab will be too far from marth to connect, and youll only tumble in front of him.
THIS, is why marth can escape with upb, and other characters, they can react then.
Normal dash grabs do not work.
Do the same thing, except right after the dthrow-
be frame perfect to dash , cancel it by holding R, then immediately grab .
no shield will pop up, but you will grab marth, right after the dthrow.
where the normal dash grab would fail.
this is how you stop upB escapes.
The shield cancels the dash, it makes ddd slide to a stop. except you dont stop, you grab.
it has to do with ddds speed after canceling a dash.
thats what shield canceled grabs are,
youll know that you did them right if you can chaingrab faster than if you used a normal dash grab.
(ill make this quick..)
Dashing shield grabs work just the same but you do not slide,
a shield pops up for a standing grab, out of a dash.
(your standing grab range is better then dashing G.range)
im still testing them due to how strange they are.
1.dash forward
2.press shield
3.hold forward(while the shield is canceling the dash)
4.press grab, while holding forward and shield.
it doesnt seem to work against upB escapes, it takes too long to initiate.
you can do many more CGs per stage length though.