best thing to do is to watch Hoarders or How Clean is Your House with them. They get to see that filth isnt healthy at all. My son used to be a pig and still has his moments however since I had him watch those shows he has figured it out. Dishes not allowed out of kitchen, his laundry done at least once a week without fail, bed changed once a week (thats his minimal laundry per week , lol)
If he doesnt do his laundry he has no clean clothes, he has exactly 8 pairs of underwear- do you think I was thinking when I did that one????