Just make sure the game saves after each run.
Here's a video of the trick, courtesy of Ekopingviini. You can also equip everything (you only need the pistol) when deploying, to save GMP and other materials. The materials will need some time to be process of course, depending on the strength of your Base Development platform, so just idle in menus afterwards. Now that you have your wormhole fulton, keep replaying Hellbound until you're satisfied with the results.
#Metal gear solid 5 episode 12 install
After beating mission 31 and completing side-op 50, which asks you to capture a legendary jackal in Africa, you will be able to install the upgrade. You can only unlock the wormhole upgrade fairly late in the game. Skip the cutscene, turn back to where Sahelanthropus is kept, take out the guards and fulton away. It takes place indoors however, so you will need to have the wormhole upgrade for your fulton unlocked. This side-op has containers of fuel, precious and minor metals. The trick is to replay episode 12, Hellbound (the one that sends you to extract Huey Emmerich).
Warning: there's a spoiler of an early-game mission beyond this point. The chapters and episodes line up to some of the Metal Gear Solid V: The Phantom Pain achievements.
A Reddit user posted a list of what potentially could be all of the chapters and episodes in the full game. By replaying a certain mission in the game, you can keep extracting resources indefinitely. A list of all the chapters from Metal Gear Solid V: The Phantom Pain may have leaked online this week. While it's generally better to focus on just what you need, having a surplus of fuel or metals can never hurt. If you've been busy sorting out your Mother Base in Metal Gear Solid 5: The Phantom Pain, you'll know that not having enough fuel can severely limit your progress. If you're running low on fuel and metal, this trick lets you farm a good chunk fairly quickly.