Riven with multishot is pretty much required (any extra damage is a bonus), because it really makes uncharged and initial shots from the bow without [Split Flights]' buff do significant damage, as well as making the number of projectiles at 4 stacks absolutely ridiculous.

[Thunderbolt] is present in order to make maintaining the [Split Flights] buff easy even if you miss as the explosions also trigger it, but a little extra damage ever hurts when you can fire 20 arrows per shot.

Spam normal enemies with uncharged shots to rapidly build [Split Flights] and saturate the targeting area with arrows, and use charged shots on heavier enemies.

Make sure to keep bow in vertical spread mode, as the negative accuracy from both [Split Flights] and [Heavy Caliber] only affects the spread perpendicular to the mode. In this way the vertical spread of the shots will be a constant, and the real significant spread will be horizontal, allowing your 20 arrows to absolutely cover your target.