I recommend WP Guru's tutorial: https://youtu.be/jROlY34tNNU?si=DCB-IKlFnw0sZt9H

It can be used to convert characters between generations easily, as long as the clone shapes are there. it's pretty easy to follow. 

I don't use G9. I tried, but I can't get a male chest that looks acceptable to me.

They modeled in a defined W shape around the breasts with a higher density than the surrounding mesh, and there are morphs or shapes out there to buy that get rid of that effect. I don't understand the reasoning behind it, because they removed the nipples and navel in favor of the quad mesh. Seems like that should have adequate for the chest as well, but it makes sense they would prioritize the gender that makes them movey.