Hi there Persons! I just had a chance to listen to the episode and thanks for the kind words :)
I'm glad you finally got a chance to try out the liner - I'm hoping as you play with it you start to find new ways to work with the product. You're right about the brown vs. gray - I have all three that they make (brown, gray and blue) and I honestly find the brown to be the most useful as I like warm shadows. I've used the blue for some models here and there but I don't think I've ever used the gray since the first few times I tried it.
Something to play with - try using the liner with different amounts of water; the behavior of the product changes as you water it down. When you get it to a more water than liner mix it starts to be very useable as a painted shadow as well as a liner. Even when doing pure lining, I always water it down a little bit because right out of the bottle it's REALLY intense.
I also find that it makes a nice 'ink' to write or trace patterns with when doing the base for scrollwork or lettering.
It's a neat product and behaves in ways that no other 'paint' I've worked with does, so I'm looking forward to seeing what you come up with.