Been ten years since I lived in L.A. and dealt with St. Augustine or Bermuda. Rather than a wall-to-wall kill, is there any kind of systemic you can apply to kill the weeds but save the Bermuda. Here in Jersey I use a broadleaf systemic to kill dandelions and other weeds and save my bentgrass.

As for a sprayer, I do use Roundup (Glyphosate) and prefer a larger 2 gallon spraker such as an RL, Gilmore, or others. BTW I stopped using Monsanto brand Roundup because the active ingredient is glyphosate and Roundup is twice as expensive as generic. I also get the highest concentration generally available (41%) which is also cheaper than the more dilute mixtures. Basically you are paying Monsanto to dilute with water.