Try gently shaking the tomato plant, and also try "finger flicking" the
tomato blossoms. I do that in the late Spring and whether it works
better than doing nothing, who knows! Haven't killed a plant by doing
so (yet). Some varities just drop blossoms no matter what. I grow
some delicious (beefsteak) every year and have a ton of blossom drop,
just the way it is.

As to BER - many think that the belief that calcium deficincy being the
cause isn't true. NOT doing anything to a plant that has BER will
have the BER go away. Neighbor of mine usually has it every year
(plants very early), does nothing and the BER goes away on the later
tomatoes. PS - he had a soil test done and the calcium levels were on
the high range and oh did he have the BER on the early tomatoes (very
cold/wet Spring 3 years? back).