Below is a previous GW discussion on BT that will give you some info to start with:

Here is a link that might be useful: BT discussion

I had to order it on line , but I live in a small town. It is germ warfare specifically targeted to Cabbage lopers. Works like a charm. I bought the liquid, that you dilute and spray. One dose took them out for the season last year.

I had to use it last winter on my Swiss chard. I use the powder form in a Dustin Mizer.

I just stick it in a canning jar that I've added tiny holes to the lid. It works wonderfully well! I just wished it worked on the baby grasshoppers now eating my swiss chard! :)