Final answer:
To sand a large set of stairs for painting, an orbital sander or a random orbital sander is recommended for efficiency and ease of control. A detail sander can be used for corners and crevices.
Step-by-step explanation:
If you are looking to sand a large set of stairs in preparation for painting, the best tool for the job would likely be an orbital sander or a random orbital sander. These sanders are efficient at removing material quickly and are generally easy to control, which is important when working on a staircase where precision is key. An orbital sander moves in a consistent pattern which reduces the chances of creating swirl marks on the wood.
A random orbital sander combines the action of an orbital sander with a spinning disc for even more efficient sanding. For corner areas or crevices, a detail sander could be employed to reach spots that a larger sander cannot. When sanding, always start with a coarser grit to remove imperfections quickly and then move on to finer grits to create a smooth finish that is ideal for painting.