Cover king car cover care instructions say put the cover on the car and soap it up and hose it off. Do not use a washing machine.

The local laundry has a self srevice dry clean machine. What do you think of dry cleaning?

I throw mine in the washer(gentle setting)Porsche script cover!
put on let it air dry. no issues

(boo hoo)

That's what I did with mine.

Do you think new scotchguard would prevent the cover from breathing properly to dry after a rainstorm?

On my 993, my Porsche cover got lots of use, and the best way to wash it was soap and water on the car. It also helped the way I used it by rolling it on and off the same way religiously...