There isn't really any EASY way to cheese insectron, especially at higher ranks of play. The best insectors tend to be ones with instant kills, like the scissor beetle that can heave enemies off of the field, and especially the ladybug with its healing skill. The easiest way is probably to save it for after the bonus dungeon and use a dark emperor, because of its infinite-use ranged skill and ability to knockback from normal attacks.
But even insta-kill attacks lose effectiveness in higher ranks, and beating Rank S twice (to get all rewards) pretty much requires a full team of 5 insectors with max stats (or close to max).
Eclipsing power is, at times, not only the instrument of demons, but also of gods.
Lost, but not forgotten.