https://zeussim.tumblr.com/post/183212990402/a-very-poorly-done-tutorial-on-how-to-make-bgc

See the tutorial under the cut…

Find the dress you want to turn into a top.

By clicking the icon you’ll be able to mark the vertices on the other side of the dress!

Restrict visibility of the nudetop by clicking the eye next to the mesh name.

Delete the part of the nudetop we don’t need.

Delete the baked layer.