Last summer I found that boiling water will kill weeds, and kills them quick. However boiling water takes time and a large individual crabgrass would take a whole pot of boiling water to kill the weed. My question asks if anyone knows of any other home remedies for weeds. Spot treatment for crabgrass is all I need. Small yard.
Instead of trying to kill the weeds as is, you could think of them as future fertilizer. Get some cardboard or newspaper, lay it on top, and start "lasagna gardening" by putting compost on top of that. You'll be able to plant in it come spring. One thing I've learned from weeds is that you can try to go down to their level, but you end up opening up the soil for weed seeds that are embedded in the ground.
Dealing with problems can be that way in life. You can choose to dwell on the problem or see it as a path to build something preferable. BTW, since the cardboard will suppress weeds below it, the new weeds sprouting in your garden will be easier to pull!
If you want to boil water for nearly free you can get a solar cooker that does this. And then get free hot water that you can use to keep killing those unwanted plants forever.
A small hand held butane torch might also work but the weeds grow up again.