I finally called a lawn service two weeks ago. My lawn full of dandelions was completely devoid of the yellow flowers and seed heads two days after they sprayed it, and a week later there was no sign of the weed at all.
The lawn service aerated my lawn three days ago and after a good watering, the grass is greener and fuller than I have ever seen it.
They will return in another two weeks to treat for crabgrass.
Unless ALL your near-by neighbors con troll the dandelions and crabgrass in their yards, your chances of controlling them in your lawn by just pulling them, especially in a larger yard, are next to nil.