Hand-Sand the Curves
Sand curved surfaces—and other areas an electric sander can't reach—by hand. Treat all areas equally, using the same progression of sandpaper grits for both hand and power sanding. Start with 80-grit to sand away blemishes, then use 120-grit and finally 180-grit. Using these exact grits isn't vital (100-150-180 works too), but it's important to progress in steps, removing deeper scratches and leaving finer scratches each time.