This LoRA was specifically designed to be used with other LoRAs. I searched far and wide for a LoRA that would increase the breast size of a character, and none of them did anything at all. This does, and it does it without altering the facial features (or other aspects of the figure) of your character.

Use strength of anywhere between around 0.5 and 1.5, but you can experiment.

This is mostly designed for clothed images. It will work for nudes, but with the variable results that you can expect from Flux.