Modeling Diffusivity

[Nileo2005]

Hello all. I am trying to model diffusivity in Abaqus, something quite different from the usual impact dynamics models that I am accustomed to working with. The learning model and an example of what I am trying to achieve would be the deflating of a helium balloon through the latex of the balloon. I've read a lot of diffusion and solubility, but am still a bit unclear of a few key points.

Firstly, can permeability be applied and utilized with shell elements, which is the ideal element for this particular scenario.
Secondly, does the mass diffusion primarily compute the mas transfered into the permeable material from hypothetical reservoirs, or can it model the flow of the helium from the inside air cavity through the wall, deflating the balloon?

Thanks for your time!