Personally I have never been successful in isolating hermies by management of organs. It simply is not that easy to do.

There will be organs formed deep into the flowers that you will never see or never get to.

I have found that heat caused hermies however produce impotent seeds and the tomatos are still very right, fruitful and very strong.

Save your self the headaches and either keep it or chuck it. If you keep it, all your shit near it will generate seeds...and if your stock is good, well then that CAN be a good thing.

Trust me...seeded tomato plants can taste very very good indeed.