This is mostly echoing tiemco. The idea with waiting 2 weeks after fertilizing is so that the weeds will be very healthy before you come in and chop their little heads off. Healthy weeds absorb the herbicide better than sickly weeds. Part of that recommendation is also to get people to stop thinking about using Weed-N-Feed products all the time. Timing is the issue with those, so fertilizing first and following up with herbicide (spot spray) later satisfies most everyone.

The first year it sleeps.
The second year it creeps.
The third year it leaps.

That is the credo for all ground covers except creeping charlie and kudzu. KBG will seem slow at first but in 2 years you'll be laughing about any setback in the first year. The herbicide will take out the weeds. Insasmuch as they might have provided significant coverage with no KBG mixed in, then maybe you will have bare spots. If so then I would suggest using good compost as a mulch on those spots. The compost/mulch will keep the ground from getting hot there and sprouting more weeds. Watch the spots for weeds and pull them as soon as you see them.

Deep infrequent watering and dense grass is what keeps the weeds from coming back next year. Bare or thin spots are an open invitation to weeds. Sometimes Mother Nature comes along with a week of rain that will sprout weed seeds. That, of course, doesn't help. If She does, then Halts or something with preemergent qualities might be appropriate.