Complex sentence: He found the filming schedule quite demanding, particularly the three weeks of night filming and a scene in which his character is attacked by a plague of locusts, most of which were computer-generated in post-production but some were real on camera.
Split into simpler sentences: He found the filming schedule quite demanding, particularly the three weeks of night filming and a scene in which his character is attacked by a plague of locusts. Most of the locusts were computer-generated in post-production though some were real on camera.