So I just saw some youtube vids on these and was pretty impressed and just bought them:
https://store.artis-opus.com/en-us/collections/dirty-downI imagine you can get them from a lot of places buy I bought them from Artis Opus.
Anyway, if you search on vids for the Verdigris and Rust especially, I think you'll be impressed. I am giving Moss a try too since I have so much rock-like terrain I thought I would try something new, but the results in the vids haven't blown me away.
But the Rust did. I love what I saw. This is more for my tank models, but if you wanted weathered up 40k terrain, like Ork terrain, this might do some magic.
When they come in and I give them a try I will do a review here. Unless someone else has tried them and wants to give some feedback.