(Part 3) Reddit mentions: The best lawn & garden sprayers

https://www.amazon.com/dp/B01DWCTSQE

Backpack with a battery used to spray weed killer.

Get about 5 of those and fill em with the strongest acid that they can hold. Spray that hairy bastard down. Go for the face first.

If you aren't getting at least 1 inch of rain a week you need some type of irrigation. Since your lawn is so huge I'd recommend installing a sprinkler system with a Rachio controller.

Bag or not to bad is totally up to you. Since you have so much to mow I would go for the mulching kit. If you like to use your clippings for a compost pile then bagging would be a good idea. I'd buy both because they both can be useful.

You can start now buy killing everything with Glyphosate. A couple applications of this will be necessary. Waiting about two weeks.
Make sure you wear PPE when spraying this stuff. After killing everything you want to scalp and bag the dead grass/weeds up.
Buy a good sprayer. In the north, cheap sprayers usually don't last a season so a good one is a worthy investment. https://www.amazon.com/Chapin-21220XP-Fertilizer-Herbicides-Pesticides/dp/B000Q3W5DG/ref=sr_1_9?ie=UTF8&qid=1499653769&sr=8-9&keywords=chapin+sprayer

3 inches is the height of cut you set your mower. Frequency like I said depends on grass type. A lot of people up north like to mow high at 3.5 or 4 inches but to me it looks unkept in my opinion. It does have it's advantages in terms of blocking out light to new weeds that are trying to grow in your new lawn.

Glyphosate kills everything so spray it on anything you want dead.

RE: The Gun

It's actually a pesticide pump, or a "flit gun." Modern pesticide pumps look completely different, but up until maybe the 2000s, cartoons commonly portrayed pest exterminator characters as practicing their trade with a flit gun (Warning: TVTropes Page) that looks kind of like the bastard child of a calking gun and a dynamite plunger. As the TVTropes page points out, nobody has actually used one of the things in real life since the 1950s, but the imagery is so iconic that Stanley, an exterminator and the main character of DK3 uses one to fight Donkey Kong and all the bugs DK stirs up by smacking their hives.