Further into the game, especially when you have multiple skill points and few resources, fast travel to the Villa Verde Alpha rally point in the Villa Verde region in Solo mode (cannot be done in Co-Op mode). You will need an EMP drone, preferably Level 2 or 3. You will also need the Grenade Launcher skill and attachment on your weapon. You can still do this without the EMP drone and Grenade Launcher, but it will be more difficult and time consuming. As soon as you spawn at the Villa Verde Alpha rally point, open your map to see the nearby “+5,000” resource convoy, east of Villa Verde Alpha. It will have one of the four resources and cycles often. Mark the convoy and the following checkpoint on the map. Then, grab a motorcycle and quickly drive to the marked checkpoint.
Drive through the river and park at the end of the fork in the road, hiding behind the trees. Quickly switch your weapon to the grenade launcher and deploy the EMP drone. Hit the middle of the convoy with the drone to stop it, making sure to not get spotted by the enemies as you are using the drone while hiding behind the trees. Next, shoot three grenades into the front and back vehicles to destroy them. Run up to the middle vehicle and kill the passenger and driver with bullets from your weapon. Tag the supplies to complete the side mission and get 5,000 resources. If done correctly, all the enemies will be dead and you can fast travel back to the Villa Verde Alpha rally point. Since you are in Solo mode, the world will reset and the supply convoy will respawn. Repeat this process as many times as desired to get an unlimited amount of resources. The entire process should take between 1:45 to 2 minutes each time. You can get between 150,000 to 170,000 resources per hour, depending on your efficiency. Note: Make sure to meet the convoy at the fork in the road. If you meet them further up the road, there is a nearby base where enemies will keep respawning from and hunting you until you escape, which adds more time to the process.