Corn gluten needs to be soaked a little after spreading, but then needs 2-3 days of dryness after the wet for it to be effective. It'll last a couple of months. But I don't think it'll keep your crabgrass from growing this year. Crabgrass will grow from previous year's seeds. So spreading CGM will help you in your cause next year, but just yanking them up when you see them will be your best bet this year unfortunately. What will also help is covering garden beds with a good layer of mulch, and keeping your lawn healthy by mowing high. It's less likely to spring up if there's no bare/unmulched spots in the landscape.

Thanks PDub, but...I've removed the grass from most of my front yard and replaced it with salvias of differing types and lantana and mulch. I'm trying to prevent last year's seeds from growing. I put down a good layer of mulch last fall and plan to put down an even better layer of mulch this month but thought that putting down a layer of CGM and watering it and letting it dry before putting down the mulch would work better at keeping the nasty crab grass from germinating. I'm a couple weeks behind you, since I'm a tad bit north of Dallas. And I don't think mulch deters crabgrass as I'd mulched areas last year that consequently had crabgrass...and I really don't want to have to be out there pulling weeds again. Did that last fall and the last two weeks! My body's telling me that I'm too old to be bent over/kneeling down to pull weeds for 1-2 hours a day!