Homefront: The Revolution

I got this easily during the main mission zero hour.

In order to have a Molotov, you need propellant and an igniter.

At one point you will get the objective "Defend the trucks whilst being loaded." You have trucks on one side and steel shipping containers on the other side. In between these objectives is a building with supplies for Molotov's if you don't have any. As the truck is being loaded, about 6-8 KPA will spawn close enough together near the steel containers to where you can throw a Molotov and kill 5+ soldiers. If you miss your chance you can load last checkpoint and try again.

If this is a bit confusing, leave a comment and let me know what you need help with and I will try my best to help you.

Spoiler!!!

After you escaped the trap at Independence Hall you have to kill all enemies around you, after that go at the right corner and prepare one or two Molotovs. Then you have just to wait and when the door opens and the enemies spawn throw your Molotov as fast as you can. You will kill more than 5 enemies.

I found a great place to get this done near the end of the campaign. It's easily done in free roam and does not require a specific spot in a specific mission.

The subway exit that you use to enter Old Town near the end of the game is at the bottom of a three story building. You simply need to stand on the roof and get the attention of the roaming airship. For reasons I cannot understand, enemies cannot figure out how to get at you up here and will stand around like mannequins with their thumbs up their asses. Only wolverines and the orange SWAT guys will shoot at you, and the rest can't seem to figure out which end of their gun the bullets come out of.

To get this achievement specifically, wait for a large number of enemies to turn up and jump down to the first floor where the gunsmith machine is. Right next to the machine is a door blocked by a piece of sheet metal, and the enemies will run right up to it attempting to get through to you. When you're sure you've got enough, toss a molotov under the sheet metal from the machine side and you'll barbecue them.

This is also a great place to work on jobs that require kill counts, proximity device kills (just toss them off the east side of the building), surviving for two minutes inside an airship searchlight, killing enemies with every weapon and modification, getting hacked drone kills, or killing heavies. There's also two traps that you can use here if you've the patience, but I've found that working on that in particular is not ideal in this spot.