this may override styles of faces a little bit, but if you use an aDetailer it becomes unnoticeable,
best results came from prefectIllustriousXL_v3 using face_yolov8n and prompt "bulging breasts, (<lora:Quad Boob:0.8>, (quadboob:1.3), bra dent)," (that :1.3 seems critical for some reason) and negative prompt "see through," unless you want the shirt to be a bit transparent
"quadboob" or "quad boob" seem to be interchangeable, i cant really tell if it matters or not.

doesnt quite work as well or as consistently with smaller bust sizes, but big, huge, and gigantic, work great from my testing!
if you cant get txt2img to work very well, drawing over an already existing image and using img2img works just as good if not better!
even if the bulging/quadboob look isnt desired, side effects from my training images also caused this to be a good lora for strained buttons, see-through tops, bra lines, and just a general bust size enhancer if size isnt specified