https://www.mycopigments.com/ also does lichen, and has plenty of guides and resources.
Just a heads up however to be mindful about toxicity of the mushrooms you select, however generally speaking the dyed end product is safe. https://pmc.ncbi.nlm.nih.gov/articles/PMC7277368/
Right, lichens are a big one. Thanks for the link!
Just don't eat any unless you're certain it's safe. You won't get poisoned just from touching any mushrooms.
One interesting gotcha that regularly kills people, is that there are some look-a-like species between Eurasia and North America, where one is edible and the other is poison. Apparently is fairly common in Washington state for eastern European immigrants (cultures where mushroom foraging is common) to die this way, because they eat something that looks familiar to them.