Try pairing these together on one button:

Firebrands
Oiled Sword
(this creates an instant crit hit with every swing)

Boomerang
Ice Shards

Electric Whip
Ice Shards

Throwing Knife
Ice Shards
(then see if you can reload Ice Shards to effect bleeding
and if you can find a colorless oil grenade, you're set.)

Throwing Knife
Sadists Stiletto
(again, instant crit hits)

Throwing Knife
Hokuto's Bow


Remember that the item in the left box shoots out first,
so make sure you get the order correct to inflict the critical hits.
It doesn't work with everything, but when it does, it's powerful.