Here is another way without having to read too much CHEAP AND CHEERFUL
use a bottomless pot , add an old pipe , few holes , line bottom of pot with light mix , line around the bottomless pot with hot mix , fill pipe with light mix , water like you would a small pot , there is a flap where i can check roots at bottom , once see them you can water slower in a circle around the hotter mix to break the soil in , makes flushing ten time quicker and more easy
handy for autos