Really depends on the dirt or varnish that is plugging them up, I'm leaning to getting a ultrasonic cleaner, I have a crock pot with a green cleaner, works on surface crud but doesn't get into the hard to reach places. I have some friends who are using the harbor freight, they say they are too small to put much in. A good sized one runs 400$ Tell ya just how deep I've been looking into one a 50$ a gal cleaning solution is nothing more than water, coloring, soap, sodium silicate aka water glass. Maybe Santa will bring one?