We do not take bookings. None of this applies.
Most of it is not about bookings. A bar's problems are the empty afternoon, the regular who did not become a regular, and being invisible to the people nearest to you — none of which a reservation system touches. That is why the tools listed below for a bar are a different set from the ones a restaurant starts with.
Discounting the quiet hours just cheapens the place.
It can, and that is a fair worry. A flat discount all week does cheapen you, and mostly it pays your existing customers to keep doing what they already did. A narrow one — this item, these two hours, these days — is a different instrument, and the part that matters is measuring afterwards whether it brought anyone new or only moved the same people around.