I learned the washing machine trick, just like clothes and adding fabric softener, from this forum and used it for years annually. No damage, and the lines are as flexible as new. For lines that you can’t remove, hand wash in a tub with laundry detergent, rinse in water adding softener, then finally fresh water. You may have to do both ends of a halyard separately.
I’d worry about hitting them with a power washer as I’ve seen them frayed on other boats, but perhaps the lines were already damaged.