You need to either:
1. Spray wait 2 weeks then make multiple tiller passes, it might take 4 or 5 passes. But I find that this is hard on the soil and causes the soil to crust when it dries up.
2. Spray wait 2 weeks, plow then disk then till.
The first couple years in a new garden will always be weedy. Get a good hoe and get to work. I commit at minimum 1 hour of weeding every night (it's usually 2 hrs). A successful garden is a direct result of how much labor you put into it, I have a 5000 SF area that produces over 50% of our households veggies for the year. Are you thinking about planting yet this year?