An alternative idea from a novice. Here's the bottom line first: I cut the mealworms in half, pour on some warm water, and shake them around for just a few seconds before draining. By the time they're served up outside, they're as wet as they'll ever be. So why? (1) Dry ones blow away in the wind, and just break when robins try to pick up three at a time to feed young. (2) Whole wet ones are tough not soft, and small birds struggle with them. (3) When halved, the water gets inside so they get wet much faster. (4) Cutting them is a faff, but actually doesn't take long; crumbling by hand just creates a lot of useless powder. (5) I wouldn't fancy eating meat that's soaked in water for ages. (6) Note: Wet ones spoil very quickly outside, so only put out enough to be taken immediately (they will be).
A brief P.S. to my earlier suggestion about just swishing dried worms in water and then draining them : if the drained worms are then kept overnight in a covered container in the fridge, they do continue to swell. Whether or not that benefits the birds I have no idea.
During the summer I use live mealworms, they are around the same price as dried. The birds go mad for them for the babies and are so much better. They now come when I call. As for dried I soak them in hot water and allow to cool, or better still I sprinkle them in the water drinking/ bird bath.