I gut them from the lower jaws to the anal cavity. Slit the backbone membrane and clean out the blood vein as well as any remaining blood from the gullet.
Their natural slime will prevent water intrusion. Then, when I get them home, I soak them in vinegar (2 -3 hrs.) which removes all the slime and fishyness. Wash with ice cold water to firm the meat and if I am not ready to cook them right away, I smother them in table salt and soak them in ice cold water in the refrigerator.
I cook them in vegetable oil with no additional seasoning, except for corn meal or flour.
No, the vinegar does not leave a vinegar taste. The vinegar is an acid which neutralizes the pH of the alkaline, based slime. The slime is attracted and drawn out of the meat by natural chemistry, and neutralizes the vinegar.
Try this out and you will love eating trout forever more, even if you don't like them now.