Please can anyone recommend scenes with women getting messy whilst showing off their clean bare soles?

The more obscure, hard to find scenes the better.

There's "A Day In The Life" from The Man and The Wife.

In the second half of the video, there's an excellent scene where the Wife is barefoot in jeans, feet propped up on a table, then... well, you'll see.

Quite a lot of TMATW's content fits, at least partially. For example, the "Feet Up, Face Pied" series tends to end with the model getting her feet messy at the end, so you do get to see her messy with clean bare feet. There are also a few with one or more models getting messy wearing socks, which they take off at the end and reveal their (usually mostly) clean feet. Though, again, they rarely stay clean for very long...