Why do feel that your Method 1 is incorrect? The results look fine It appears that you first found the Thevenin equivalent of the voltage source and first two resistors and then applied superposition to find the final Voc. Nothing wrong with that.
In your Method 2, it's not entirely clear to me what your steps were trying to accomplish. It appears that you were again trying to use superposition to find the contribution from each source, but for the voltage source you found the total current that it produces, not the portion flowing through the shorted output.
The method that you employed in the first attempt, namely working section by section through the circuit making Thevenin (or Norton) transformations can be very useful. It can allow you to combine sources easily as you go. Try it for the Norton equivalent: first convert the 25V source and 5 Ohm resistor to its Norton equivalent. What's then in parallel and can be combined? Rinse, repeat