I did use stable diffusion to generate a single frame, then it transitions between the original size breasts and the new much larger ones. Then a lot of animation work goes in to animate it correctly so it looks like they're not just an image pasted on.
I'm sorry there's no jiggle, but I really just focused on the growing out of the shirts. Redgifs compressed it pretty hard, but the left shirt gets thinner as it streches out, was pretty proud of that. Perhaps next time I'll figure out how to do it while a bra is being worn, that'd be cool.
There's a faster version in the mega folder if this one is too slow.
There are two versions, one I pushed much further than normal and things start to shake / fall apart a bit.
I always wanted to do a growth in a shirt that streches it to the point of sliding out.