I take mine to my local dry cleaner every April - $35 bucks. Every year he says “how much did I charge you last year?”. Kind of funny at this point.

I think spray it with Starbrite with a garden sprayer.

I did end up stuffing mine into an industrial washer with a little bit of bleach and a lot of soap. Worked like a charm.

I was told industrial washing machine with Oxyclean. Never tried it though

Years ago I was told to use Woolite as the detergent. Laundromat with large machines to wash. To treat with waterproof, I would think the easiest way is to get one of the thin rolls of plastic from the hardware store and cover the boat to protect the boat, then put the cover on over the plastic and spray with a pump sprayer.