I have to admit to not knowing abouit the soaking pre planting too.
Have added to mine this autumn, but after all the rain we've had the soil was very wet, not damp! Makes sense as they do like water meadows- think of the ones in Oxford, wonderful sight.
Am lucky though, as have mine in an area of my part shade garden where there is some clay soil. I noticed last spring that they have spread to an adjacent border, which is dryer- definitely didnt plant any there.
Lily beetles are a pest, I just try & catch & stamp on as many as poss. Some years worse than others. J.