1. Size - because you're going to lengthen brass in a FL sizing operation. That amount of lengthening will vary a little. The purpose of trimming is to get them withing spec and the same length.
2. Trim - just the most logical time to do this operation
3. Anneal - because sizing work hardens the brass. You are re-tempering the brass. If you size after, you are defeating the purpose of annealing.
