[3X24SPD]

My bare T-111 sided shop was about 15 years old & looking pretty sad & weathered- probably about the same as what you're describing.

About 5 years ago, I had my buddy Jeff who is professional painter get after it.
I hit it with a power washer first, and it brought it back amazingly. Looked almost new again.

Think it still looks pretty good IMHO, 5 years later.
Might have him put another coat on it next year or two.

Jeff's got a sweet looking barrier blue Tripower 66 GTO.
You might know him if you're in our area of the NH seacoast.
I'm sure he'd give you a good deal as one of our local pontiac brethren.