Marsha, I am sorry, I cannot give you a detailed answer to your question, as we do not bag blossoms. It is not practical to do on our scale, and actually not necessary due to very low pollinator activity in our tomato growing area.
Bees have plenty of other flowers to get busy with - we have clover, lophantus, blooming kale, onions, and many flowering herbs close by. I actually have problems with cucumber fruit set because our cuke's GH is behind tomato beds, and it is also gets ignored by the bees up until this time of summer.
Still no fruit set on eggplants!
