I have a 60 gallon sprayer with the folding arms for the back of my tractor. I usually spray every spring with 2-4-D and I generally don't have any crab grass or dandelions. The trouble is that nobody around me sprays for weeds and I get my yard re-seeded in weeds every year from the wind blowing their seeds into my lawn. Oh well, I'll just keep spraying. I like a nice looking lawn.
Another thing I do as well is to mix malathion into my weed killing mix. I have a 1500 sq. ft. wrap around porch and we like to spend time out there in the summer as well as around the pool area. By mixing in the pesticide with the herbicide, I kill two birds with one stone. We can pretty well sit outside in the evenings and never get bitten by a mosquito. Also, the dogs basically never get any ticks or fleas. Sometimes I have to spray again in the summer when the darn Japanese beetles begin to emerge. They can swarm and literally defoliate a decent sized tree in a day. They seem to like my oaks in particular for some reason.
I have plenty of kudzu in the woods that I fight constantly, but they don't seem to care for that at all. It figures!
I guess I'm a bad boy to the no chemical crowd. I can say that I did try most all of the no chemical methods, but with a 10 acre lawn, it never worked. If I had a small lawn, I could probably keep up with just pulling the weeds and dandelions. Heck, for the first year or two I lived here, I bet I pulled over a thousand cockleburr (
http://kaweahoaks.com/html/cockleburr.html) plants. The Shelties I had then would always get loads of those things on them and I would have every finger bleeding trying to get them off. Those weeds suck!! They were the main reason I bought my 3 pt. sprayer. They were winning the battle with me.