Snake is fat as ****.
Anyways, the key to this MU is to space at a distance that allows you to react to a dash attack/mortar slide. If you space our normal dash grab spacing, you're put at a range that makes our option obvious (any time you run in Snake will probably spotdodge. Or he can just ftilt) and that gives him two options that we can't react to. Thus, you'll be spacing a little farther than normal at neutral.
Personally, what I like to do is camp a little bit if Snake's set up a good rhythm for his own camp game. Once you mess with it just a little, then I move in to the spacing I described above. From there, it's just making reads/reacting to a dash attack or mortar slide. Keep in mind that Snake usually feels more threatened at this spacing than we do, and that it's entirely possible to punish a nade toss (at least when it's done from the normal way of releasing the B button) with a dash grab at this spacing. It requires some good reaction time, so make sure you're looking carefully at Snake and NOT at yourself. That's also another really important thing to do, in any MU, really.