Since the grass can't use fertilizer when it's not growing, I'd seed first and only fertilize after the seed comes up.

Thxs, then should i see in begining of March and fertilize 6 - 8 weeks later. Is March right time frame in CEntral NJ.

at123

Actually, August or September (as soon as the heat of summer breaks) is best. For a spring seeding, put the seed down as soon as the soil temperature is around 40F. You need to base it on conditions, not calendars.

BPGreen's advice hits the mark.....grass seed is fed when the grass can use it and that is "when its growing".
Let the soil warm up before spreading grass seed and it can be a help to turf when you give it something the grass will want to grow in.
Make a point of giving to your lawn, 1/2 - 1" of compost or good topsoil. Look to improving the draining aspect of your lawn. Putting compost down in spring invites the seed to grow and improves the soil it is living in.
If you were to do this annually, spring and fall, you would improve your lawn immensely and the bare spots you see, would fill in much better.
FErtilizing when its called for will also fill in bare spots. A high nitrogen type fertilizer applied when the soil has warmed up will encourage grass to grow and fill in those bare spots.
But, its never a mistake to do overseeding where it can improve the lawn and increase defense against disease and pests.