No idea what Dawn Dish Soap is but no doubt it can be substituted with something pure and simple here in Australia.
There's a few comments about how nothing will grow again where this is sprayed so best use it on those weeds growing in the cracks of cement for instance.
That is the best suggestion of all Susanne! I have some ground hugging weeds growing between the cracks in my cement and I will use the boiling water. Loathe to use week killer like I did in the "old days".
Soap rather than detergent?
We've found pure el cheepo Vinegar applied with a narrow paint roller to be totally effective against a fine-leaved sedge. The plants die and we've noticed Carpet Grass growing keenly over where the sedge was. And that's in our back area laughingly called a 'lawn'. So far, so good.
Novel idea. Bit like Elaine's boiling water trick only high tech. Wouldn't want anything flammable or animal to be caught in the blast.
You'd need to be careful where you pointed the wand. I can see sheds and fences crackling away and major conflagrations in suburbia.