Those "nasty, slimy things", cooked in the shells, are the things I remember from my childhood, when we would make summertime trips to FL from NJ, and on the back roads through SC and GA, there would be these old black guys on the sides of the road with a large steel drum, boiling the peanuts in them. My Dad would always stop for some, at several places, coming and going, then when we'd get to my grandmother's place, she'd have some for us, boiling all day, and really slimy! Back then, and probably still, in some areas in season, the green peanuts in the stores were still soft, maybe harvested the day before. It wasn't until decades later I could find raw peanuts around here, and only shelled, though occasionally I see them in the shells, but they are totally dried out. I just use the shelled ones.
Mom and Sis didn't like them as much, probably because of the sliminess.
Those Hawaiian boiled peanuts remind me of a Cinese version, with some star anise, but also some black cardamom, which gives it a delicious flavor.