Plastic bags for VB's work great!
I'll use VB's in combo with a ski touring set up. I don't use VB foot systems often, but when I do, here's how I do it.
I use the really super thin plastic bags that come off the roller from the produce isle at the grocery store. They eventually break, but you can usually get two days out of one bag.
NO LINER SOCK, the bag goes right on my bare feet.
Then a medium thickness wool (or wool blend) sock.
I do this to keep my ski boot liners dry, no other reason. But, when I stop hiking, my feet cool off fast, so I need to change out of the plastic bags and into a regular sock system. If not, I get cold feet.
I like keeping the liners dry, it's a big plus on a long trip. They don't freeze at night.