I have no experience with BSF but I am interested. I have chickens, worms, a horse, and an ever-growing garden! My neighbor has BSF and about 500,000 worms working throw-out scraps from the food bank.
I would like to feed BSFL to my chickens. Happy wormin' Pete

Here's a link to a previous thread with lots of info

Here is a link that might be useful: All about Black Soldier Fly

"Question: what shall I do with the BSF when the castings are ready to harvest? Way way too many to separate out."

Screen your vermicompost at 1/4" and you'll separate most of them. Use 1/8" screen and you'll get 'em all. If you don't want to screen, then store your VC in a well-ventilated, covered container so it stays moist and warm. This gives worm cocoons and mature BSFL time to hatch. 1/2" vent holes around the top of the container will give BSF hatchlings an exit.

Older grubs will look dark, but can still consume food scraps. Once they are fully mature, they lose their mouth parts and try to find a good place to pupate. They can still move, but they don't eat. Finally, once the fly hatches out, the dark shell remains. All these look alike on a casual glance.

Andrew

Thought I'd mention a new blog : Raising Black Soldier Flies - Tips and techniques for raising black soldier fly larvae (Hermetia illucens)

Fairly new buts lots of good content. The author is raising BSF in a green house over the winter in Florida.

Here is a link that might be useful: Raising Black Soldier Flies