You have a very high standard here
I got the idea from Bret Contreras. Here's what he said:
AN INCREDIBLE DEADLIFT AND OLYMPIC LIFT ASSISTANCE EXERCISE
When an assistance lift works, you know it immediately. I never got any "assistance" from swinging light kettlebells around. However, several months ago I bought a 106-pound kettlebell, and more recently a 203-pound kettlebell.
I should mention that my form on kettlebell swings is far from optimal. I look like a damn Neanderthal heaving the weight around. But I know how to use my glutes properly (from 6 years of hip thrusting) and therefore I fire them like crazy during the swing.
I've found that it's easy to swing 70 pounds with perfect form, but when you go heavier, it's a different story. Eventually I'll make the 203-pounder look right, but in the meantime it still provides an amazing training stimulus.
I'm not nearly as eloquent as Marianne, but nevertheless I've found that the transfer to deadlifting is incredible as long as you go heavy. At first, "heavy" for a typical female lifter might be 35 pounds and for a typical male, 70 pounds.
However, over time, fit females want to strive to swing 106 pounds for reps and males should shoot for 203 pounds. This may seem far-fetched, but it's a long-term goal to strive for.
In the video above, I'm swinging the 203-pounder for 8 reps. Two weeks later I got 20 reps with it, so your strength and power will rapidly increase when you start taking swings seriously. Now my 106-pounder feels like a cupcake.
Best still, heavy swings don't destroy the body like maximal deadlifts do, so you can train them more frequently. In fact, you can put deadlifts on the backburner for a while and maintain your strength by doing heavy a#@ swings 2-3 times per week.