[Zeke]

Put spacers blocks front and behind your cove blade to move it over. If you have the model with the fence, just move the fence out enough to get the blade over the shape you need to cut down. You will still have a small area to sand. You could also use a block plane to knock that down to nearly flat and finish with a scraper cut to your final molding shape.

Look up scratch molding. If you're going 100% carpentry before sandpaper was common, remember that carbon steel and sharpening stones have been around a long time. But, so has sandpaper, it just either wasn't widely available or was too expensive. Or both.

Scrapers have been around since glass was made. Used on wood floors centuries ago. Card scrapers are easy to modify on the bench grinder and touched up with a Dremel.