From what I hear form the Australians I know most Australians don't say those things.
Drop bears are a lie conceived to scare hapless tourists.
Everyone should be afraid of drop spiders!
no aussie say's "Strewth" or "flammin galah" just as nobody say's "strike a light"
very old people might say "galah" (idiot, clown) but certainly not flammin and people from the sticks might still say g'day.
but the rest are straight TVism's used as a substitute for swearing.
for those unaware Alf is not meant to be a nice old bloke, he's meant to be a stereotype of an old yobbo, but being on at 7:30 means he can't swear.
as such most of his expression are G rated versions of regular Ocker expression's
So while british people might hear "stone the crows" and relate it back to the english expression "stone me" (if they even use it anymore) in actual fact when old Alf announces his many variations of "stone the crows" it's closer to the expression F me or F me drunk. then some quaint local expression.
and anytime he use's a random word beginning with F, it's basically the same as saying "firetruck" around an 8 year.
and you don't throw a "shrimp" on the barbie (a shrimp in aus is someone whos a shortarse) we call them prawns (technically they're yabbies), the ad said shrimp so overseas viewers would understand the expression and "snag" is the most common term anyway "throw another snag on the barbie" and you'll still sound like a deadset ******* idiot if you ever say this anywhere other than a barbie. and even then just don't say it australian english is lazy as ****. as such expressions get shorter and shorter. nowadays if you're at a barbie you'll just be asked if you "want another" or "want some more" "still hungry" etc, etc. (in which case just say what you want or if don't want anything just say "nah thanks", "nah", "thanks anyway", or "nah i'm right thanks". and if you are invited to a barbie it will be "you comin over for a barbie?" "come round, we're havin a barbie?" we won't go out of our way to make sentences longer.
also nobody drink's fosters, It's export only as the domestic sales went ******'s up, most due to the fact it tastes like cat's ******.