BTW, the sheild-cancelled grab is quite a bit slower than the dashing grab. If you already have them in a grab, I suggest just dashing grab, since they can't get out of it.
Against Snake, it's easy. See if they know how to get out of the chain grab with grenades. If they do, make sure you are always in the 4th slot, since the grenades will send the snake upwards, NOT YOU. That's important. Make sure you stay out Snake's range, because he can give you a poundin'. However, Snake has two really big weaknesses: First, he can get gimped really easily by D3 via cypher grab. You can set this up easily with the chain grab. Secondly, Snake SUCKS when getting juggled in the air, which is something D3 is good at. Try doing a fast-falled nair to the ground followed by up tilt to launch them and then read their air dodge to tech chase them with bairs. It sounds complicated, but it's not too tough. D3 is one of Snake's more annoying match ups.
Here's a good video for it:
http://www.getyourtournament.com/multimedia/2008/07/family-fun-arcade-aero-vs-dsf_14.html
DSF is one of the best players in all of SoCal so, it's not like Aero's playing a scrub.