In her youth my old lady long-haired mog would basically leave for a few months over the summer where, presumably, she spent the entire time climbing through hedges as she'd always come back with some absolutely stonking mats. Typically we'd trim them back as far as they'd go and that would be it, but some we'd just have to do what we could and then let them grow out a bit before taking another go. Bathing them was a firm no but I think it might have helped smaller patches.
Our tactic these days are strategic trims of her problem areas before they can create a problem, and this year we will be getting her professionally almost-shaved before summer after a health scare last year (not an option for pigs I know). She's not a huge fan but the regular trims are much easier than the mats!