Hi,
The only way to deal with this situation is to vigorously rake the dead areas removing as much of the dead material as possible and opening up the area so soil is exposed. You can then apply a little soil (topedress) apply seed, rake lightly, water well and either use a mulch to keep the area moist or make sure that water is applied in a timely fashion. Doing this will insure that you have a good seed bed to accept seed and giving it the best chance to germinate and grow.