Don't spray a
weed control now. If you read the label you will see you are not supposed to reseed for in most cases 6 weeks with most over the top selective
weed controls. Since you are planning on re seeding anyway, you may want to opt to spot spray using Round Up. This will kill any plants it comes in contact with (including your lawn) but you can re
seed with in a week,, with no bad results. Just try very hard to limit your spraying. so you don't wind up with more dead then alive lawn.