Dogs "scoot" when they need their anal glands expressed. They have glands in their anus that help them pass waste and form time to time they become blocked or filled and need some help. It can become very painful. Take her/him to a vet or a groomer, they will know what to do. You can do it yourself, but it is not pleasant to defile your own dog. As far as the scratching, dogs do have allergies and can have dry skin. Bath them with quality shampoo but only as recommended for that breed. Too much or little can cause more issues. Best bet, take her to the vet, spend your $50 and help them out. If you were suffering from the same issues you would go to the doctor ASAP.