I used to wear the hakama that you mention but these days usually wear
Bu Jin Design's 100% cotton hakama or an indigo, cotton hakama from
Iwata.
As far as cleaning goes, I usually only wash it about once every four to six months, if even that, really. I fill a tub part way with warm water, put in a bit of detergent, and swish the hakama around for a while, then I rinse it. I hang it up to dry afterwards for about a day then iron it to get the pleats back in nicely.
As far as keeping the pleats nice during day-to-day wearing of the hakama, I think the secret really is in learning how to fold the hakama correctly. Although the instructions included with the Bu Jin hakama are pretty good, there are minute nuances that you need to be aware of, I think.
I start folding my hakama with the front down. I line up the back pleat then flip the hakama over to the front. I then work my way from the back pleat (all the way "inside" the hakama toward the back) and make sure that all of the "inside" pleats are in place. Most people (including myself for a while) just fold the front pleats and forget about the ones in the back... One other thing you can check is to make sure the "crotch" flap which is, actually, on the inside of the hakama (if you lay out the hakama with the front up and lift up the front panel, you should see the "crotch" flap right inside) should "lay" down nicely, too.
I was taught the above by someone who, incidentally, was in charge of ironing and folding the hakama at Bu Jin Design.
It's much easier to show than type out, unfortunately. I'll be happy to show you if we ever bump into each other...
-- Jun