It could be he's allergic to weeds and grass. Another reason some lay and lick their feet is out of boredom. They need two good long walks a day, and a lot of other stimulation. They are terriers, and this means energetic!
As for grooming, it's like having a new puppy. You have to take it just a tiny step at a time all the while "cooing" and talking softly and giving hugs. Don't make the brushing a long one. Just a few seconds and end with a treat. Brushing teeth is the same way.