During "Return to the Hall of Heroes", use the doors behind you to enter The Hall of Heroes. Once inside, exit to the Plaza to cause items in the Soldier's Field area to respawn. You can use this to your advantage to farm gear. Go to the Plaza and defeat the Vox and Founders. You should also use the sky-lines to travel to the lower Gondola Station and defeat the Founders and Fireman. There is also a Motorized Patriot in its entrance hall. Just stun it, go to the elevator, and use it to return to the Soldier's Field boardwalk. Find the toy store next to the carousel and lift its shutter to enter, then use Shock Jockey on the generator near the locked door to open it. This allows you to collect a piece of random gear. Return to the Hall of Heroes by using the elevator and the sky-lines. Enter the doors to the museum. Once inside collect the Salts and repeat the process.