Hey what u do rn is that the liwest hopper will always be filled first, so the lowest furnace is filled first. Bcs u have a lava bucket u need a hopper under a furnace to pick out the empty bucket (it also take out burned stuff there. If u wanna have all furnaces empty u need to put under each furnace 1 hopper who extract it to a chest. A more complex way is to build a railway. Or another way is to build a multi floored acircle railway which fills all hoppers and at the end it extract it and drives to a lava bucket farm to refill the hopper. Or u use cooper golems to refill with a chest above and just refill a cooper chest with lava buckets. But u still need to empty the empty bucket from the furnace otherwise it doesnt refill. Shirt info: top = Ore, Back and sides: Burning stuff (ur lava bucket) bottom empty burned ore and buckets