I am lazy.

What would be the fastest way to model a Teflon coating for the "top" of this muffin pan either as a derived part or as multi-body solid and get the volume of the Teflon?

So solutions thus far require too much work (picking).

Reference

https://forum.solidworks.com/thread/36721?q=Teflon%20Coating

Here is a parametric way to do it. It takes a couple of features, each with a couple of selections, but it is fully parametric so if the geometry changes or more cups are added, it will still update without reselecting faces to thicken. The radiate/knit technique was originally designed for mold design, but there are numerous uses for it in other types of modeling, especially when you need copies of complex sets of faces.

I hope this helps,

Jim