This method is great, I never had Shindo on my team and it works so well that I even got Kurawara, the cop to max trust. Simply you will meet Amada and will be knocked out by Cain, you will awake in a trash area and this will be the first time you encounter zombie scrap heads. Just go through the level killing them, always try for headshots. You will come to a point where there is a door with red handles one on each side. Shindo and Kurawara will turn them to open the door, at this point you will have to defend them as zombie scrap heads will come and attack you. It is a narrow hall way and they will keep coming. A lot will come, just go for headshots and try to kill as many as possible. If you have upgraded your electric shock and its capacity you can use this to kill multiple of them at one time. This is great because they drop a lot of electric shock recharges. I feel it is still better to go for headshots and doing so quickly. You can keep doing this even after the door is open. The enemies will eventually stop and you can continue on. Soon you will again come to another door exactly the same as the one mentioned above. Only this time the enemies are infinitely spawning and there is 4 ammo boxes. Just sit back and keep going for headshots and quick kills. You will Max trust Shindo in no time.