Can I get an explanation for that last one?
I’m fine! I’m finer than frog fur!*
*Frog fur of course is so fine you can’t even see it.
One can conclude that you never owned a microwave oven. 
“Dumber than a ditch carp”
My grandmother from Kentucky was well known for losing her reading glasses and then remembering that she’d pushed them up to the top of her head. Then she’d always say, “If they was a snake, they’d have bitten me!”
I’m busier than a one-legged man in an ass kicking contest.
“Don’t go visiting with both arms the same length” - I’ve never heard it before, but I assume it means don’t go to someone’s house empty-handed. Bring a gift.
That’s what I think, too. I read it somewhere, and don’t remember where, unfortunately.
Here’s a couple more, courtesy of my grandmother on my father’s side:
All fools aren’t dead yet.
What they won’t make to take your money.
My father’s measures of scarcity:
Like hens’ teeth
or, if my mother wasn’t around:
Like rocking horse shit
My father’s version of this was: Use your loaf. It was decades later that I realised that this was actually rhyming slang (“Loaf of bread”). We were not cockneys - both my father and I were born and raised about as far from London as you can be and still be in England. But my father’s father was born in London - so maybe that’s where he got it from.
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As nervous as a long-tailed cat in a room full of rocking chairs.
Get an education or you’ll end up picking bird shit out of cuckoo clocks for a living.
“Busier than a one-armed paperhanger.”
“I should hope to kiss a pig!”
“Reach me down [some object on a high shelf.”
“Even a blind chicken picks up a grain occasionally.”
“You got a tree full of owls.”
Slicker than snake shit.
Of a womanizer: He’d fuck a snake if he could get someone to hold its head.
Colder than a well-digger’s ass.
Cold enough to freeze the balls off a brass monkey.
Colder than a whore’s heart.
Colder than a husky’s nuts in a dogsled race in Alaska in January.
Hot enough to boil a monkey’s bum.
Oh! and “All crapped out?”, usually addressed to a cat that is deeply, deeply asleep after a busy day of napping.
One of my favorite songs.
or like a screaming herd of turtles, one of my father’s gems.
Was your grandmother Fred Mertz?
This one came out of me spontaneously one day when my boss was lavishing me with praise, some part of which I felt was insincere. “Oh, save your butter for your toast.”
Said of of the socially maladroit: “He took the express train through childhood.”
“I wouldn’t pay that much to see a pissant eat a bale of hay.”
“I wouldn’t pay that much to see the Statue of Liberty take a crap.”
Re post 51: I knew a guy whose parents’ way of urging him to study was to say, “if you don’t get good grades, you’ll wind up being a shit shoveler in the circus.”