We've been to the Grand Canyon twice. Both times we followed I70 to St. Louis, then I44 and I40. We wanted to include Carlsbad Caverns and White Sands, so got off the Interstate at Amarillo TX to head to southern MN. We rejoined I40 at Albuquerque.
For Petrified Forest and Painted Desert we stayed at the KOA in Holbrook. Between there and the Canyon we stopped at Meteor Crater, then took route 89 north out of Flagstaff so we could visit
Sunset Crater Volcano and
Wupatki National monument. We then took route 64 into the east end of the Park, stayed a night at Desert View CG (no hookups) and then spent two nights at Trailer Village.