How to have consistent soft body physics in a specific area of an object using vertex groups? I'm trying to add soft body physics to a small vertex group within a larger object, thus applying the soft body behavior to that small area of the object.

My end result will hopefully be an exaggerated gooey collision response with a collision object piercing the mesh at specific areas, but have the rest of the object remain firm and unresponsive.

I have made two vertex groups, one group for the specific piercing area and one for the inverse, that both have gravity setting at 1. When I set the specific area vertex group as the Soft Body and Soft Body Edges group it causes the gravity 1 to make the specific area unresponsive to the soft body physics and the inverse group to giggle. This is the opposite result I want. I then change the inverse vertex group to be the Soft Body and Soft Body Edges group and, in tests, this has created the effect I wished for, but not consistently. In the test phase, with simpler meshes, this seemed to work. Now, with slightly more complex meshes, it is not working.

Any insights into how to secure the specific piercing area vertex group to be the only area responding to the soft body physics would be helpful!!
I know this is an old post, but I thought I would contribute anyway. First you have to go into weight paint mode and paint the parts you would like to be rigid and assign this to a vertex group. This means that the parts you want to remain firm should be completely red. The parts that you want to be jiggly should be green or yellow, not completely blue (if it is blue, then it'll act like a cloth). Then go to the physics menu item on your object and add a new active rigid body and soft body. Under the soft body goal, turn the default goal strength up to 1 (this will make certain parts of the object completely rigid). Then, in the same area, set the vertex group to the weight painted group you made earlier. Bake the physics and play. PS. I'm working in blender 2.78