Yes, it is safe to spray Drive XLR8 Herbicide when there is no forcasted rain within 24 hours.
Drive XLR8 Herbicide should be applied 24 hours after it has rained and when there is no rain in the forecast for at least 24 hours in the future.
Drive XLR8 Herbicide Crabgrass Killer should not be used on Centipede turf.
Your dilution rate depends on what you are specifically treating. Please see the Drive XLR8 product label for diltuion rates (see table starting on page 7).
Per the Drive XLR8 Herbicide label, it is only labeled for foxtail grass.
A better option would be Tenacity Herbicide. It is labeled for goosegrass, foxtail, and nimblewill. It is recommended to spot treat with Round Up in areas where the orchardgrass is growing.