It's not always easy, but if you can plan circular routes, or even out-and-back trips, the first few times, you don't have to worry about getting the number of days right or making some arbitrary pick-up date. Since you're starting and finishing at your car, you can plan 8-10 miles per day, If you finish early, you don't have to wait around. If you find you're slower, you're not inconveniencing someone by making them wait around. After a few trips, you'll have the planning part figured out. (I'm assuming you're driving yourself to the trailhead.)