I have sprayed just ahead of the drills with good results. However, I have had poor results by spraying right after seeding. I get better weed control by waiting three to four days after seeding. I try as much as possible to let the combine do all the residue management. They pick through and spread any clumps of straw.
Cattle also do a good job of cleaning up the grass on the headlands.
The only time I have any problems is on fields where I have had lodged crops. Heavy harrows are ideal to clean up lodged crops. The problem I have is that I don't have access to a set of heavy harrows and I really don't have the horsepower to pull them. I bought a set of tines that mount on the shank of the cultivator. The tines were originally designed to help level furrows and seal up the field when using anhydrous.