Any product with 2,4-D will beat them down. Look at labels closely.We have alot of rain this year in Milwaukee, WI. Every year I apply fertilizer w/ crabgrass control, but this year I have ALOT more dandelions. I have been just spot spraying them w/ ortho weed b gone. Anything else I can try because they are multiplying.
Generally, the liquid spray is more concentrated than anything you can get in granules.
Do not spray them directly with RoundUp. It will kill them, but will also splatter on the grass and kill it.