Sand smooth. Apply damp towel to all and let dry... this raises little bits of fibers you can sand off again with finer sandpaper or steel wool.

Apply a stain as per product's directions. Basically, wipe on and wipe off. Let dry and then lightly sand with steel wool. repeat if desired. Usually one or two applications are enough. You may want to use a product first that preps the wood so the stain flows and colors evenly.

Apply a varnish or lacquer a per directions. Use steel wool between coats and a tac cloth.

I would normally recommend Birchwood Casey Tru-oil, but not sure how well it goes with grey or black stains.

Don't worry about it. This type of stock can be easily sanded and done again.

I just covered mine with Duracoat. Took about10 mins with an air brush. Turned out great.