The manufacturer recommends taking the herb directly from the garden, shaking or brushing any dirt off & dehydrating immediately. However, I find that with our sandy soil there always seems to be some grit left after dehydrating. Therefore, I always rinse the herb off (in this case Thyme) and then pat it dry on a papertowel before using the dehydrator. There is nothing worse than biting down on a grain of sand.
Once it is dry (follow the manufacturer’s instructions on heat setting and time), you will take each stalk, pinch it and in a downward motion go all the way down the stalk to remove the little Thyme leaves. Warning: this is very time consuming and somewhat of a pain. However most recipes that call for Thyme use a very small quantity – so a little really will go a long way.