Hi, I am redoing a section of lawn for a customer. it is filled with weeds and pretty much no grass. in the past I have spread topsoil on top of the grass (about 2 inches) and seeded and the other seed comes through. however, i am not sure what to do in this situation. if i rototil the weeds and the soil i am afraid that it will cause weeds to come in. If i spray the weeds then reseed i think i have to wait a couple weeks before i can seed? what would be your approach to this. it is about a 15x40 foot area. should i just dump topsoil on top of everything? please give me your suggestions. thank you.