He basically pairs a Transformer shield with a grenade that does continuous shock damage, like the Hex or the Stormfront. Each tick of damage done by the grenade counts as a tick of splash damage for the purposes of Means of Destruction. I discovered this myself when messing around with the Echo, a Torgue pistol that only fires sticky rounds, but each round explodes three times (I was lucky enough to get a double penetrating version off of a Loot Tink, so 6 explosions per trigger pull).
I dont like going into Bottomless tree, i feel like it gives almost nothing, since for most part im just throwing granades. Shields of Ret give survi and some dmg.
As to granades i found out this cute little nade mode from Vladof with singularity that lay 6 sticki nades that expode when enemy is near. And this little thing have only 121 dmg, but becouse of 7 explosions it does compared dmg to others that im finding, less and less as times fly but i love the singularity thing that pulls enemy to granade and im yet to find another one with this mode. Im lv40 btw