Here are some overlooked tips for chemical spraying.
1) You want to read labels thoroughly. Many grass killers require the use of crop oil. Some herbicides need surfactants. Glyphosates you should be using liquid or dry ammonium sulfate with it.
2) Spraying when temperatures are too cold or too hot result in poor herbicide control. Contact herbicides work best when a plant isn't "stressed" and is actively growing.
3) Products like glyphosate shouldn't be sprayed on forages that recently was clipped. It would be better to spray glyphosate and then wait4 or 5 days to clip or til down the dying materials.
4) Nozzle tips matter. You want to have a spray pattern than contains as many tiny liquid molecules vs large one's. We want a high pressure, really fine mist. If we "drench" the plants you get poorer kill. The liquid is less likely to stick as it will run off the leaf or plant surface. Get a mist on there and you will see a huge difference.
4a) If you have the choice between spraying 10-15 gallons of water per acre vs 20-25 gallons, you will tend to do better with a lower volume of water. Get the right set up to get a high pressure mist and better overall coverage.
5) My clients see a much better burndown when they apply liquid seed starter at burndown or use foliar plant foods over the top in combination with glyphosate. The humics in there acts as sticker spreader and the blend changes the water pH which helps with control.
6) healthy soil with the correct pH range results in better chemical control. This is because healthy forages and weeds also die faster than stressed one's with products like glyphosate.