Use straight needles or a short circular to work the long narrow border, then switch to a long circular to pick up the stitches for the body. If desired, change to shorter needles as the stitch count decreases.
Border stitches in parentheses (k1, p1, k1) are worked into a single stitch, in this case into the yo from the previous row. This creates 3 stitches from 1 (double increase).
To keep track of the RS when working the garter body, place an optional locking marker on the RS of the shawl.