You can download a final example of a dragon wingbeat here
The basic idea is simple:
-first you bind your geometry to your skeleton (or whatever, this works equally well with blendshapes).
-then you select the surface that should have 'floppy-skin'
-and create softbody.
!!Make sure!!! that you use 'Duplicate,Make Copy soft' and 'Make Non-soft a Goal', this will let the softbodies follow the bound skin with respect to the goalweight of each CV/Particle.
-then select the created softbody-surfaces and go into component mode,
select the CV/particles and set their goalweight using the component editor.
Alternatively you can use the Paint Attributes tool to paint the GoalPP values.
1 makes it stick to the original surface
0 makes it totally disregard it
everything inbetween makes 'floppy-skin'.