I don't know about pleats.
If the skirt isn't acrylic you may want to start a different thread, or being pleats you may get a better response even if it is. A title of "blocking pleats" would more likely get you people who've been there and done that.
For ribbing, I avoid steam blocking no matter what the fabric is or method used. (Hard to put wet socks on a stretcher without stretching the ribbing, which is another reason I like to steam my wool socks.)
If the yarn isn't fuzzy at all I would think about pressing the pleats in with steam (pressing the head with the steamer on the Jiffy really flattens out the fuzz and it looks bad).
I would definitely try some swatches (block, then wash, stretch and typically any type of abuse you can think of) before doing any method. Different methods give different results and it boils down to personal opinion, like me liking the "killed" acrylic from steaming.