I soak all my plants during watering, and only during that time. I use plastic bins that I fill up with my preferred solution (usually water since I'm lazy), and dunk the pot in it slowly. To prevent excessive floatation, I'd water from the top before sinking the pot slowly into the bin. I use PrimeAgra now, which doesn't float up all that much. I still water from the top as I think it helps bring fresh air into the pot.
Water & fertilizer are too annoying and expensive, respectively, for me to use only once. After a certain number of plants, the washed out "schmutz" and charcoal dust or whatever build up and I toss the water and fill a fresh bin.