I have to assume your lawn is KBG, and from what you've described, the lawn has already been overseeded. Doing more of that won't make other types of grass go away. But in any case, the way to assure an evenly formed and "perfect" lawn is to tear out the sod and start over. Some lawn companies call that a "renovation." A lawn that is full of weeds and problem grasses may benefit more with a compete do-over -- if you absolutely cannot accept the yard as it is. I recommend inquiring of a professional lawn company for doing renovation; it may be a little more pricey than do-it-yourself, but, in the long run, complete grass removal and reseeding done the correct (and guaranteed) way by professionals will give you the aesthetics and peacefulness of mind you're looking for.