I remembered the missing lines from the second verse... here is the whole song:
^^
Late last night, my grandfather got me out of bed.
He had a look in his eyes like I never seen.
He said, "Go to the kitchen, boy, and get me some matches.
On your way outside, fetch me some kerosene."

Then we went to the barn and cut the horses loose.
We scattered the pigs and the chickens, too.
Then he soaked away the potion and said, "Gimme a light, boy!"
I said I was scared, he said, "That's OK. This is gonna be fun!" and

Hey we burned the barn down last night!
Felt so good that it didn't seem right.
Grandpa started laughin', said, "To hell with that old barn!
I ain't never seen so much LIGHT on this old farm!"

She started crackin' and the flames burned to the sky.
The volunteers came they said, "Christ! What happened?"
My daddy stared and my momma cried.
My grandfather looked at me, and we just about died laughin'!

Hey, we burned the barn down last night!
Felt so good that it didn't seem right.
Grandpa started laughin', said, "To hell with that old barn!
I ain't never seen so much LIGHT on this old farm!"

The coals cooked down. They put me to bed.
My daddy whipped me and my momma told me to pray.
Grandpa came to my window and said, "Your grandmother's crazy, too."
When the mornin' came, they came and they took him away.

Hey we burned the barn down last night!
Felt so good that it didn't seem right.
Grandpa started yellin', "Get out the way! You block my light!"
Hey we burned the barn down last… ooo we burned the barn down last…
Hey we burned the barn down last night!