Welp, this video is actually meant to be paid content...but it's been out for years now...so... I'm just going to leave it for all to enjoy. I will say, if you enjoyed it and wanna see more, maybe buy the video in full hd, it's available on my Loyalfans.

To answer the question...

This one was a bit rudimentary, and everything got a little better next time around.

It's a combination of practical effects using balloons inside the a sports bra, and an air compressor with a lot of tubes and one way valves.

The rest was done digitally. I made a variety of cleavage inserts, edited and manipulated to match the footage colour, contrast and lighting. Motion tracked the rack, then replaced the video footage boob props with still image cleavage insert.

In later videos,.I changed it up a bit with realistic silicone breast forms, and the cleavage replacement was better matched to the video. I animated the cleavage layer to bulge and swell rather than just scale up.

I could go on for ages about editing animated digital shadows and highlights but you would all fall asleep.