Use a hose end sprayer. The proportion is not too critical. Dawn is a little thick, sometimes it won't dispense very well depending on your particular sprayer. Get some sudsy mix spraying and just eyeball it. I cut it 50/50 with household Ammonia. Figure a pint (or 16 fl. oz) of detergent and another pint of Ammonia for a smaller typical suburban front yard. It should then be watered in, though I doubt it would hurt anything if you didn't. I wait for the radar to show a good line of thunderboomers and apply right before a rain or just water it in lightly off the turf blades.
A long time suburban lawn will benefit from this. What it does is reduce the "surface tension" of the soil so that rainfall or irrigation is better absorbed and retained, versus just running off. Just try it and see what you think, you should notice the lawn holds its green for a longer time after a rain. Best time is probably right before Summer begins in earnest, and the typical drier climate of July and August. Moderate fertilization in the fall with proper nutrients as well is what sets up the turf fir success to cruise through a dry hot summer a whole lot better.