laudry machine. i always bring my blankets to the tack store. they offer a special cleaning service.
i know this may sound sketchy but a launders mat! it has never let me down and usually the ones i go have pretty big sized washers! if you can't find any other places to wash them you can always get a huge bucket and wash them by hand! (but that can be a pain and take a lot of time.)
I drop them off at the laundry place and run before they see the water turn black😂