Here is a commission I did featuring breast expansion!

Another recent commission I did where the client asked for breast expansion and then a lactation edit. For this one I roughed out all 3 stages first to make sure the proportions were right. I draw on a gray canvas so when I'm copy/pasting it to show a client I erase with white. Its invisible when sent but on the original canvas it looks a bit silly.

After it's roughed out I reline it. This one the process was a bit different, so I painted the background first which included the giant fluffy tails and then I went into rendering.
Normally I use multiply layers for shading, but for this piece I simply locked each section of color and shaded/highlighted on the same layer. Then afterwards added a blue rim light. Once the base body and background were done, I simply painted over the base figure to do the alts. 

Here is a recent commission I did! Included is a process shot to show how I managed to get it to what it is.
First I pose 3D models to help get a general feel for the where things are and how they should look. 
Second I rough over that and tweak things to fit the vibes for the piece.
Every step of the way is communicating with the commissioner as well so that they know the direction its going and to make sure that everything is a-okay.
After that its the usual for lining and rendering!
With the BG I tend to only paint the portions that you're going to see, so without the characters it looks a bit silly.... When everything is completely rendered, then I do several color layer modes and textures to adjust to satisfaction.