This is a one-on-one thread, no? lol
Been gone a few days, sorry so late to reply...
Yeah, I don't find fungus gnats too much of a problem, but that doesn't mean I don't try to kill them off... just that they're kinda easy compared to other pests. The populations can go crazy if you don't keep on them though, assuming you can't get rid of them permanently...
Spraying the top of the soil works, though you don't really want to do it everyday. A product called Tanglefoot is great... yellow sticky gel for trapping pests. I've lined the rim of pots w these & it catches the gnats, along w other pests. A good barrier to isolate an area as well, just watch out for it... stepped in once... just wipes off.
Don't know about a "soil wash", perhaps just meant a drench... terminology...? After I spray the adults, I like to soil drench w an oil product to hamper the larvae, then spray again in a few days, then drench, then should be gone, unless an adult was missed, then they'll pop up again in a little. You'll likely kill them off though... until another one flies in from the outside & takes residence again... lol. Such is life. Peace brother.