1. This method is only available during one of the first story missions called Gaining Credence, the Electronics won't spawn anymore after you progress past the objecitve "Find out who was screaming", this is right after you're sent to the pumping station and defeat bandits. After defeating bandits, you can loot as many Electronics as you want as long as you don't progress to the next objective.

2. It's always possible to change back and forth the story missions using the Advanced menu, you can access Advanced menu by going into your Main Menu > Play > The Following > Save, so you don't have to worry about missing this. However if you reset your story, depending on the story mission you choose, everything that wasn't available after that story mission will reset, except your driver skill-tree, buggy, character skill-trees and inventory. This means that you'll have to redo every single side mission, hive, recapture safe zones and etc, in The Following. Resetting The Following's story doesn't affect Campaign.

3. If you're past the main mission Gaining Credence and the objective "Find out who was screaming", the only way to access this method is resetting your story back to The Way Out, it'll take around 10-15 minutes to reach the point where you can farm Electronics. Therefore this is the best for those who hasn't yet started The Following, or those who don't mind losing 100% completion.

4. It's possible to change the story back to The Way Out, farm Electronics and then bring your story back to 100% using the Advanced menu. After you've finished The Following's story once, you can use your Advanced menu to change your main mission. However this will force you to redo the final mission again, and it won't restore all the side missions, safe zones and etc, therefore you'll have to redo it all in order to reach 100% completion again.