ENGINE FLANGE
I would avoid using any type of abrasives on the machined surface of the engine block
oil pan flange (iron or aluminum block, goes without saying alum is more sensitive to scratches), block flange has a machined surface with a specific surface finish by design that you dont want to damage or alter to keep a good seal. To mechanically scrape the silicone off this flange, try using plastic scrapers (like the body shops use for bondo or other uses) you can cut them to size if needed. Final prep with a solvent to clean the surface (I know this it tough upside down with
oil dripping!) before the new sealant bead goes onto pan for re-install.
OIL PAN FLANGE
The pan in your gallery seems to be a custom one but with a stamped steel flange (upper portion), these are more forgiving as far as surface roughness but try to avoid abrasives here also and use plastic implement here too when removing old sealant.