Sorry to chuckle on this one, but my aim is to grow food in any space that I can find. So if I was at F's house, I'd be ditching the lawn and replacing it with a garden of some sort. Get rid of the crabgrass? Wow, I'd get rid of ALL the grass!
Now let it be known that I do indeed have grass on my farm. I use it for two purposes...
1- mow it to feed the livestock
2- mow it for grass clippings to use as mulch.
The only weeds I remove from the pasture grasses are those that the livestock don't like. Otherwise anything goes. I don't know if I have crabgrass here in Hawaii, but I do know that I have far worse grasses to control in my gardens. Back in NJ crabgrass was my friend. It made a green lawn that never needed watering or fertilizing. I wasn't into lawns, so if it was green, it was ok by me. Yes, I had lawns. Everybody did. People expected lawns and never gave it much thought. But at this point in my life, growing food is more important than growing an ornamental lawn.
For a short period of time I had a bit of a lawn up by the current house. But I came to my senses and dug it under. The spot is now growing seed potatoes, bean seed, radishes and beets.
Back to "F".... I don't control crabgrass at all, nor wish to do so.