I thought it would be a good idea to establish a fan-made guide here on MC. Feel free to post anything that can help anyone to get through the game.
I'll start off by giving the tips on the boss battles.
It's a Small World Clock Tower Boss.
Redemption: This takes a lot of time and effort. You'll need to use paint on both of its hands. Once they are both fully painted. Then you can hop on to it's hand and it'll take you close to the face where you'll paint the face. That will end the fight and your paint capacity will increase. Remember that what you do in each boss battle will raise your paint or thinner capacity.
Destruction: All you have to do is to completley thin out both arms. Eventually the clock tower will fall apart creating a pathway to the projector screen to Mean Street. Doing this raises your thinner capacity.
This involves a lot of effort. You'll have to avoid his thinner projectiles and then block his discs. Hitting a disc will cause it to hit Pete. Then you'll have a clear shot at his back. Hit him with either paint or thinner.
Paint: Filling his tank with paint will turn him back to normal and he'll give you the rocket part.
Thinner: Filling his tank with thinner will cause him to be destroyed. The rocket part will be there where he once stood.
After you either redeem or defeat him, return to Pete on Mean Street for a reward.
If you go to the very top of Skull Island, you'll encounter Pete Pan, a Pete version of Peter Pan. He'll tell you of his sprite (Epic Mickey version of Tinker Bell) being trapped by Captain Hook on his ship.
Once you board his ship, you'll have two options to deal with Hook.
Free the Sprite: You'll have to make your way to the top of the masts and you'll find the sprite. Break the cage to free the sprite. Then Pete Pan will engage Capt Hook and your free to get the rocket part. This will increase your paint capacity
Defeat Capt Hook yourself: Time to change up the story of Peter Pan. Remain on the deck and change up the track layout. Each time you hit a wheel, he'll spin through the track that he's on. You can either cause him to hit the door to the rocket part, or to the crocodile (haven't attempted the crocodile myself though but I think it's possible.) This will increase your thinner capacity.
Return to Pete on Mean Street for a reward concerning Pete Pan.
The Mad Doctor:
This takes paitence due to the many beetleworx soldiers there. All you need to do is to destory each machine in the attic. This is achieved by thinning out the red eye on each machine. When you destroy one, it sends a shockwave that hits the mad doctors hovering vehicle. Keep doing this until the cutscene triggers.
Not sure if there is a redemption part but thinner capacity is increased after the battle.
The Shadow Blot (small one)
I put "small one" because the blot you fight isn't the actual blot, but a dripping of the actual blot. You fight him the same way you fight the huge blot monster that you first encounter in Tomorrow City. Be sure to avoid all thinner he throws at you. At times, he throws various other blot creatures at you, destroy or befriend them, your call. When he tries to suck you closer to him, throw paint or thinner at his mouth.
Paint: For a comical ending to the boss battle, hit him with paint. You eventually make him a friend and he eventually leaves. This raises your paint capacity.
Thinner: Filling him with thinner eventually kills him. Increases your thinner capacity.
Thats all for now.