This isn't so much a guide as it's more helpful information while doing this. You may want to consider using a character with Groh's fighting style. It's fast and tears through enemies. When doing a 2nd play through with a new character you still have access to any weapons and items you unlocked on your first play through but not the gold. It will take a few hours to burn through just the primary stories (marked in red). Also if you want to skip through the dialog you can hit start and select skip which is a lot faster than just hitting x over and over. While skipping it will stop at any decisions to make and then after making your choice you can skip again.
During my first play through I did all the good choices and on the second I did all evil