Biggest trick really is to prevent them early on and you won't have this issue. I had my summer with caterpillars, and that's all it took to ensure I was ready for the next outdoor season. Spray BT early in the season, and/or when you see your first moth in the garden. As soon as I see the orange looking moth(Sachem Skipper), and the cabbage moth I start my applications. I spread them about 2-3 weeks apart and I alternate with
Azamax. I was fed up with bugs in one of my tents with mothers so I used
Azamax every 10 days and they were gone. I'm also not opposed to using the No Pest Strips as long as they aren't a permanent fixture.
I'd figure out when you see them the most during the day and try to spray then, as they have to ingest the BT for it to be effective.
Cheers,
Crom