Years ago we used to fish a diving minnow for Atlantic Salmon. You simply fead the leader through a live minnow, tied on a hook, put a pinch on lead in the minnows mouth and fished it with an lift and drop action. The minnow would spiral down and the take was usually at the end of the drop.
There are many small plastic minnows on the market today.Some resemble steelhead fingerlings;since steelhead are cannabalistic it should work Has anybody tied these plastic minnows?