The best way to wash thinsulate is not to wash it at all. The shoe-grade thinsulates were not really intended for frequent cleaning, and a T400 suit can get heavy enough from being soaked that it will literally tear itself to pieces in a washer or if you try to hang it up to dry. And the slightest bit of detergent or other residue can destroy thinsulates insulating value and hydrophobic abilities.
Suit manufacturers often recommend non or low agitation washing using water with a little vinegar in it rather than a detergent, or a very lean mix of a no-residue detergent (available from sports and backpacking stores) and water followed by an extra rinse. Then let the suit drain for a while, well supported, before trying to hang or dry it. I like to wash and rinse it a tub not a machine, so the suit is well supported and can be minimally agitated without stressing it.
They also often recommend airing or spraying with an odor killer like Febreze rather than washing, whenever possible.