I’ll hit you so hard you’ll get a speeding ticket going through Draggerton (a community about 15 miles away)
can’t be jawin with you, gotta be makin a bean
Couldn’t find his ass with both hands and a map
you’re like a man with a paper ass
you got jello for brains and shit for jello
tactful as a handgrenade
My father said the first part of that, except he just edited down and said “if dog bunny.”
My grandpa used to say “Cheese and crackers!” as a swear word. Always made me laugh. Which always annoyed him. 
Not something dad said a lot, but I did hear him say it jokingly a few times.
Cheese and crackers got all muddy!
In the factory, especially in the Toolmakers’ shop, “government work” meant a job done as a favor for somebody. On the other hand, one old guy working on a road-building crew told me that the margin of error on a road curve was “plus or minus three feet.”
My husband (a grandparent) is fond of “I might have been born yesterday but it wasn’t last night.” Puzzle that out!
I chattered once when grandma was listening to one of her stories on the radio. “Hark!” was her way to say “Shut the fuck up!” She only had to say it once.
An aunt who didn’t like to swear would say “sunny beaches” for “sonsabitches”. She wouldn’t say shit if her mouth was full of it.
Oh. On the subject of people who are inept, Dad had a couple of favourites, one bluer than the other. The clean one was “S/he couldn’t organize a chook raffle.” although why gambling for livestock was considered easy is beyond me. The other, far more entertaining one, was “S/he couldn’t start a shit fight in a two-hole dunny.”
Well, I thank your grandpa for that because I’m going to borrow it. I work with children and definitely have need of a swear word I can use at work.
Couldn’t organise a piss-up in a brewery is another along those lines.
One from my Dad when he was exasperated with any of the six of us–
If your brains were gasoline, you wouldn’t have enough to power a pissant’s motorcycle around the rim of a dime.
It’s much older than that. “I swan” is a truncation of “I swan to goodness” which is the watering down of “I swear to God.”
I still say “Well, I swan!” as an expression of exaggerated surprise.
From my grandmother, born in ~1918 in South Dakota:
Expressions of surprise: “Oh my stars and garters!” (Often contracted to “Oh my stars!”)
If something is askew, it’s “skiddywumpus”, or “skiddywumpus goofy”.
There are more, if I can think of them…those are definitely ones that I’ve not actually heard outside our family, though.
I never knew either of my Grandparents to employ any colourful turns of phrase (or swear at all, for that matter), but I do have some older generation friends here in Australia who are a great source of colourful aphorisms:
“Couldn’t organise a piss-up in a brewery” (Completely useless person)
“They’d show up for the opening of a paper bag” (Media whore)
“Hungry enough to eat a horse and chase the rider”
“Flat out like a lizard drinking” (Either really, really busy, or doing bugger all, depending on context and tone)
“Like looking for a fart in a spa bath” (Attempting something with almost no chance of success)
“A can short of a six-pack” (Someone who’s not very bright)
Entire books have been written on Australianisms, now I think about it- the thing is, you don’t hear them all that often anymore (almost nobody says “Strewth” or “Stone the Crows!” these days, for example)
One that sticks with me from my grandfather was “I would rather owe it to you than beat you out of it”
My maternal grandparents:
Bugger, bloody and 'ell - this one used several times a day whenever anything irritated them.
Flamin’ yanks - this one used whenever anything remotely related to Americans irritated them.
They were exactly not the most positive, upbeat people in the world.
Well, I’ll swan! 
That’s no doubt where the ad people got it from.
An’ a quarter to his balls!
The way she does it is the way we were taught in English class and the way I’ve heard most often. The other way is a byproduct of digital watches and I usually only hear it from people who want extra accuracy.
My maternal grandmother had a set of “said the old woman who…”- expressions. They’re fairly short and to-the-point in Swedish, but I couldn’t manage to translate them that way.
“It’ll even out!”, said the old woman who shat on the bicycle saddle.
“That’s a lot of screaming for a little wool!”, said the old woman who shaved a pig.
“It’ll resolve on its own!” said the old woman who shat in the sink.
And then she’d go “heh heh” in a slightly frightening fashion that only can be reproduced by wild-haired grandmas whose nose and chin almost meet.
My mother’s favourite was always…
“I see said the blind man to the deaf man”
When we were talking nonsense
I was quite an inquisitive kid (apparently) and my nan, forever pissed-off by my constant questions would answer my, “What’s *THAT *thing nana” with, "It’s a wigwam for a gooses bridle".
The other (grand)parental ‘none of your bloody business’ retort was always, "Going to see a man about a dog". For many years I lived in hope of getting a new puppy, but alas, was always disappointed.