Using dformers on specific faces
I read some time ago about someone wanting to move some specific faces on a head. The idea was that you could create a group of just those faces and apply the dformer. The dformer would then only show the hightlighted vertices in that specific group on the head. This was some time ago, I did not bookmark it or "absorb" the info when I read it. Has anyone heard of this and how do I do it?

Comments
That sounds like you mean using the Weight Map mode with a D-Former. If that's the case, you can just change Influence Mode to Weight Map. Paint the weight with Node Weight Brush tool, then manipulate the D-Former handler.
As I recal there was nothing about weight maps and more like making a group. Kicking myself for not copying the method.
You're selecting parts of the mesh either way. I think Crosswind's suggestion of using the weight map tool allows for softer edges (instead of a hard in-the-group/not-in-the-group boundary) and less chance of messing up the original mesh.
I had a boss who reworked an electric timer system for greenhouses. The technician who sold the timers dropped by to see how we were doing with the new system and was blown away by all the bypasses that Matt (manager) had done to the timer to get results he wanted. The technician was blown away because Matt was doing things that the company had no idea you can even do with that system. Technician took pictures and went his way.
This is what some person did here in this program, the end result was faces and it's vertices on a body were singled out and the dformer now only could be applied to them and only them. It would still pull on vertices directly connected outside that "group" (lacking a better term for it) but the end result is if you need to adjust areas, say a single tooth, that could now be done without having to make a morph in blender and that movement is now keyframable. That keyframability is the real party trick. So yeah I remember there was nothing about weight maps involved in this proces and hunting anything down in the daz forums is like trying to find a needle on mars. Oh well, I will figure something out.