Complex sentence: The cockerel will then be sacrificed by slicing its neck and its wing feathers are pulled out and brushed onto its bleeding neck after which each feather is placed as sacrifice ("genselan") onto each of the offering sets.
Split into simpler sentences: The cockerel will then be sacrificed by slicing its neck. Its wing feathers are pulled out and brushed onto its bleeding neck after which each feather is placed as a sacrifice ("genselan") onto each of the offering sets.