No need for blue-water sailing for Moog and Oog...all that these early invaders needed to do was follow the coastline in boats/rafts first going north along the east coast of Asia, then east along the area of the Bering Strait (with or w/o the land bridge) and then south down the west coast of North America.
Or they could have simply followed the currents to S.A. or N.A. as the Jomon in present-day Japan did 20,000 years ago. They likely used the same techniques as Polynesians used to navigate the Pacific - follow the currents.