Seats? Dense foam padding cut to size and then material. Similar to how these dinette chairs were padded:
Use Old English dark tone polish and scratch cover-up.
Usually a furniture polish conceal most small scratches.
They sell furniture crayons and pens. You might consider trying them. Sold at hardware and home improvement centers as well as places like Target and Wal-Mart, Bed Bath & Beyond, and even larger big box grocery stores.
You can rub it with an oily nut. You can also buy a set of marker like things for all colors of wood and different color fillers if deep. To see what I mean look on Amazon.
use a kit https://www.amazon.com/Vanitek-Total-Furniture-Repair-System/dp/B0759MYP7X/ref=asc_df_B0759MYP7X/?tag=hyprod-20&linkCode=df0&hvadid=216559542401&hvpos=1o2&hvnetw=g&hvrand=7327462845236245456&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9030100&hvtargid=pla-369194408382&psc=1