Merry Christmas everyone!
When I have a problem that requires the plant and potting mix be treated, I have found that it works best to really soak the potting media and roots. In order to do this I wrap my pot in tin foil and fill the pot with the treating solution - then I leave it for about 20 minutes to make sure it has soaked into every part of the root, potting medium, and since I use clay pots, the pot as well. I top off the pot after a few minutes as the fluid does get absorbed. Then I take the foil off, let it drain well and put it back in it's spot.
I have found that if I just rinse the plant and pot with the solution, sometimes it does not get into all the crevices and such.
Just another tip I have learned.
Again - Happy Holidays!!
Steve