Add the maximum amount of population in the "Performance" menu before starting the game.
On the first day, rush your way to the loud house to the East of the map, located to the East of the Library (which is closed on Monday). Go inside and get the dog treats.
Go back to your spawn point, select the dog treats, use "X" to throw one on the ground, as close to your dog as possible. As soon as he eats it, attack people, so the dog eats them.
Repeat the process until you run out of treats. Re-load the last check point.
ETA: 10-15 min.