Walk behind the RV before entering the mill.

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When in the mill walk up to the saw blade hanging on the wall.

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After you get up from the bed walk over to the unicorn poster on the wall. After you look at the poster you can tear it off.

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When grabbing the tools for david, as you take the tools out of the toolbox the graffiti option should appear.

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When you get to school head to the left side. There is a wall you can draw on.

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After you grab Rachel's belt, head straight into the changing room and you'll see a Tempest Poster

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When you get on the train move the crate you're supposed to sit on. Now that the crate is out of the way we can explore that section of the wagon. Have a look at the wall and the graffiti option shall appear.

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Look at the statue behind you.

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When you have to smash things in the junkyard, smash the pole and then the cans of red paint. Don't smash anything before you do this.

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Look at the poster on the seat in front of you, then move it. Now you can interact with the graffiti option but we have no marker. Look at the wine bottle and take the marker.

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Complete episode 1

Before meeting mom in the school parking lot there's a white car with a box of lights in it.

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In the junkyard there is a boat. When you try to climb onto it Chloe fails to do so. To the left of the boat is a pallet you can move, now you can climb up the boat.

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After fixing up the car in the junk yard you can get this one.

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After chatting with Rachel in the car Chloe goes to her junkyard hideout.

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When you're in Frank's RV he asks you to get his notebook. When you're looking for that look at the shopping list on the kitchen counter.

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At the dormitories walk through the wet cement.

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Once you've lured Samuel out of the janitor’s room in order to grab his keys, look at the white door.

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When you get into the dormintories enter the first room on the right. This is Elliot's room. Snoop around in his room and read his journal inside his computer desk. Now you can erease the whiteboard outside his room and graffiti it.

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After you're forced to participate in the play check the mirror in the dressing room.

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In Rachel's house look at the piece of newspaper on the fridge. In order to graffiti it you gotta help Rachel's mom to get her to move away. When Rachel's mom asks you to light the candles you can get the graffiti done. Don't actual light them yet as that will start the dinner cutscene.

[Thanks @Roland for the correction]

Mind you, the crossword puzzle on the kitchen counter is not a graffiti location.

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Complete episode 2

In Rachel's room look at the map.

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School planner on Rachel's desk.

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There's a picture on the shelf to the left of Chloe's desk.

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In the bedroom of Chloe's parents immediately to the right as you walk in is a calendar.

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When fixing the car in the junkyard blow out the air filter. It is important that blowing out the filter is not the last part you repair or you won't have the option to add the graffiti.

[Thanks @linnoff for the info]

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After getting the candy bar out of the machine you're supposed to interact with it again and the graffiti option will show up. For me this didn't appear immediately. If that happens walk around a bit and it should appear.

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walk towards the exit of the hospital and you'll come across a wash your hands poster.

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If Drew is in the hospital: challenge him for his pudding. If Mikey is in the hospital: play tabletop with him. After you've finished, ask to sign the cast.

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In Rachel's dad's office open the left drawer in his desk.

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Grab the knife stuck in the wood beam and move the metal sheet.

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Complete episode 3

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Complete all 3 episodes.