Product review (1 stars): No messy at all - but BIG, BIG RIPOFF
Please save yourself the aggravation and expense.  It's not worth it - IT DOESN'T WORK.  I read the reviews and decided to buy it for my two Air-O-Swiss units at home.  With their little kit and container, it's a breeze to get the granules into the casing.  Easy and clean and quick.  It worked for less than a day on one of them and for a week on my other.  Waste of my money.  Will be a waste of your money too.  As soon as I purchased the standard replacement carts, it was perfect again!  Hey, try it and be fooled too.  Penny wise, pound foolish was I.