>>51040671I'd imagine they would shower the skin and hair coat/scales.
As for the fire, I think they would try to not put it out. Or maybe they can put it out for a moment to wash throughly. I repeat, FOR A MOMENT. I think the fire exhausting from them is just a natural action due to power output, so trying to hold it could be dangerous.
Also, they don't need a boiler, they warm the water themselves.