Fungus nats sure can be annoying in the past I had great results steaming the soil or putting boiling hot water through it .I have seen farmers with steam guns walking around there field steaming the soil so in an agricultural sense its a common practice as you know letting the soil go dry helps but not the easiest task when outside when it's raining.A lil hydrogen peroxide in the water helps fry the eggs an putting cut potatoes on the surface draws em out after all these are root eating insects .
I haven't heard of the steam gun idea.
Sounds effective, but with my small pots ... I'll cook the roots.
Dish soap helps too I hear... but never when in flower
I've heard of dish soap to go with other products as a spray,
but not sure about using it straight.
Does it just sticky up their wings and legs??
After my last trick of spray with diatomaceous earth, I don't want to.
Read some sites that said it was okay,
but it bleached and damaged the leaves of a couple of plants.