To make the lichen edible they are soaked in several changes of water, better, several changes of water with bicarbonate of soda added to each soaking.
Another method is to soak them with hardwood ashes.
The modern version of that is to soak them in a 1% solution of potash.
A method used in China is to boil lichen for 30 minutes and then soak for two days in several changes of water.
After discarding the soaking water they are boiled and that water discarded, or they are steamed.
They are then ready to eat, plain or mixed with other things, or dried and added to flour or as a thickener to soups.
Remove moisture by dabbing with paper towels,
dust with rice flour or cornstarch,
immerse in hot oil.
For moss or slivered garlic I would recommend 325°F.
E- What a long winded recipe for:
1) Soak your moss or lichen in water and baking soda (3/4t soda/pint water)for a full day. Change the water every four hours..
2) Dry it completely with towels.
3) Heat a good frying oil (peanut or blend) to 325°F.
4) Coat your lichen with corn starch.
5) Cook until tender.