Haha yeah I've been abusing those. So far I've found 3:
- Elevator at the end of Chapter 2. Infinite monkeys will spawn.
- Tsar Runner boss battle. You can prolong the battle as long as possible by only hitting the boss when neccessary. Infinite green robots will come to continue supporting it. If you shoot the robot instead of the transport pod trust is raised among all present members.
- Right before the elevator at the end of the section with Shindo and the other guy. Enemies keep spawning. There's so many enemies along the way though you'll probably max both characters even before reaching that point though.
There's probably more, but those are the easiest ones to abuse and you don't really need any besides those 3 to max all characters.
Other than that the goal is to headshot and melee enemies as much as possible, have teammates revive you and save your kits for reviving them and grabbing the trust % gain increase nanomachine from the NPC in Shibuya district.
With all that, maxing all crew members(
) is not only obtainable, it's actually really easy :s