Dexter told Delilah that life is not just fun and games. He explained that cats have chores to do just like humans do. He said that one of his favorite chores is to wash Dad's forearms. It is a daily job and is so much fun it doesn't feel like work.
He gave her instructions on how to do this job, so that she can be his backup when he is unavailable. He explained that first you have to get a good grip on the arm. If you lie on your back it can help because then you can hold on with all 4 paws. This steadies the arm and allows for very vigorous licking. It also helps if you have a long tongue like Dexter's. Delilah's is a bit short and it will be much harder for her.
He explained further that you must always lick in the opposite direction of the hair growth. You don't want to slick the hairs down, you are aiming fluff them up. One nice bonus is that after Dad plays tennis, he tastes nice and salty.
If you need Dad to move his arm so that you can get at one of those hard-to-reach spots, just use your back feet to give the arm a few well-placed kicks. It works every time.