I will be sanding the skirts flat. I finished one last night, It's alot of work!
IMO flat looks better. Especially with a high gloss black, the textured finish would show up.
I got away with sanding less of the door strips (these were not totally smooth), but due to the larger, flatter area of the skirts, I will spend the extra time getting them smooth.
You need to be careful when sanding, to rub across the skirt, not along (which is easier), in order not to leave grooves of ripples from uneven sanding.