I actually remember this product - probably due to its insane name: "Psssssst" (give or take an "s"). Off the cuff, I can't think of any other onomatopoeia brand names (although, isn't there a cleaning product called "Kablam"?) - so that earns it some sort of historic cred.
However, I think the main interest here isn't the name, but the fact that it's an "instant shampoo". I hope users of this product realized they weren't actually cleaning their hair, just spraying a Febreze type scent to mask the dirty hair odor. Yecch. A realistic ad would have had the girls hair getting flatter and greasier as the week wore on.
Another theory (as I nor anyone in my family used the stuff) is that it was similar to the Talcum powder used in the fifties and sixties. Instead of shampooing, you'd rub the powder in your hair and it would get rid of the grease. (Sort of like throwing sawdust on vomit).
I will mention that most people didn't wash their hair every single day back then. It wasn't till the eighties, I guess, that it became a sign of bad hygiene to skip a day or two. FYI Most homes didn't even have blow driers until well into the seventies. This image is from 1977 if that gives you an idea of what we were dealing with back then.
This next one is from an 1980 issue of Cosmo.
These man hands don't seem to be doing a good job of touching the hair. They're grabbing for the back of the neck..... like they're pulling the girls heads downward- like they want her to -..........uh, oh. You, don't think it's the guys saying "Come on, touch it" do you?
"Indola" is Italian for "I hate the ozone layer". That cloud above her head isn't mist from that high pressure Indola burst she's sending to her head, it's an actual chunk of the ozone layer that's fallen down from above.
And here's a few more vintage hair ads for the road....