During the fireman training, you will visit four zones: two areas outdoors and two indoors. Collectibles are the same for all of the areas. You can move freely between the first two areas, whereas the remaining two are off limits.
The first zone
After you have transported the T. Rex and talked to Vinnie, you have to go south and join the fire brigade. After a short cutscene, try to obtain a new disguise.
First open the garage door with the brick. As the astronaut, use the crate inside (after it has been rebuilt) and you will receive bricks necessary to build the color swapper. Paint red the door to the other garage, in the missing spots, and the other lever will also activate. The locker with fireman disguise is inside.
Now, use the fire extinguisher to put out the flames. It is most convenient to stand by the flames themselves and hold down the attack key while aiming at the fire. After that, pick up the hatchet thanks to which you will be able to open barricaded doors that your prybar is helpless against. Pick up the valve behind the door, mount it onto the hydrant and shut it down. Walk over to the next zone.
The second zone
Your next task is very simple. Using directions, tell the trampoline men move around to save the firemen jumping off the building. Next, to put out the fire, you will use water cannons. You have to extinguish a total of 9 fire sources, using two individual cannons. Aim exactly into the fire, instead of slightly above it.
After you are done with that, a door with a crate behind it opens. Carry the crate over to the right and build a ladder. Climb it to the building's rooftop. There, behind one of the brown crates, there is a radio controller for a car with dynamite. Drive the car across a small hole to the next area on the right and steer it into the highlighted spot. Finally, as a fireman, walk up to the cat and get it down.
Building interior - offices
Enter the building. Approach the firemen playing with extinguisher, to the distance of several steps and wait them to make space for you. You have to complete a minigame. Within the specified time limit, you have to fire the extinguisher at clown faces (in continuous fire), to pump the balloons above their heads. The balloons inflate slowly and only when the faces are turned towards you.
Walk over to the upper floor and go to the commandant office on the right. Destroy the armchairs at the window and you will find a spot to scan. Follow the footprints to the right and you will find a key in the locker. Open the door next to you. Enter the office and start smashing the objects and you will get bricks to build a trampoline. Jump up and over the lamps, reach the boss's office on the right. To jump over from the last lamp onto the office's roof, use the chicken disguised as a farmer.
Break the window and jump into the office. Open the safe and take the key. Leave the room and jump down, where you open the door to the lower level.
Building interior - basement
First, approach the grate and destroy the objects on the wall, where you find a spot to examine. Footprints first lead to the fridge, where there is a valve. Mount it onto the platform and, after you turn it, you will get higher and walk over the grate. In the next area, destroy the big block to make the astronaut crate appear. You will gain access to dynamite.
Return to the first room, blow up the grate, change the color of the paint gun and disable the button in the other room. Now, ride up on the platform and make it over to the third room, behind another grate, using the chicken, disguised as a farmer.
To leave the last area, first destroy the boats by the grate and rebuild the catapult. At the other side, fire at the button and swim back. You can now force the door open. Get on the boat and use the water cannon to fill the small reservoir to the left of the gate, with water. This will open it.