I hate crab grass
You got to find out when the pro's start laying down pre-emergence(not spelled right but?)
I use a bottle sprayer that hooks up to my hose. Its got bradleaf weed control & crabgrass stuff in it. Firsy week of 70's or over & I spray my yard. And like darkminion stated wait 2 to 4 weeks & hit it again. But again must be over 70. It's been 2 years now & quite happy with my results. 1 or 2 spots this year but,?.
Good luck.
Nik