The best plan would be to get you grass seed don now and water it as need to get it up and established now before winter. Then, in spring, you can use crabgrass preventer and your new grass will be mature enough to withstand the crabgrass preventer. If you wait until Nov./Dec. to dormant over seed, the crabgrass preventer will also prevent your over seeded turf grasess from sprouting as well.