@OP: jjj
"Detail Sprays"...may/will...have/contain:
-A type of cleaner/surfactant---(are they the same as what's in
shampoos, detergents, dish-washing liquids?)
-IPA
-Distilled water
-Polydimethalsiloxane(s); or, polyaminosiloxane(s)<<<(Are these the same?

)
-Emulsifiers
-Propellants (if pressurized)
-Even...
(drum-roll)...Silicone/Polymers!!
(J/K
)
If you'd like to experiment...
Try a recipe (into a quart-size container) with just:
-A couple of three drops of your favorite "surfactant-liquid" (if your lucky...it may already have some
"poly's" in it)
-Around 1/2 cup of household variety IPA
-Fill the remaining container-void with distilled water
-This mixture should be shaken (
not stirred!) well before use.
-(Please post the results. Thanks.)
OOOPS! If I had a recipe: "do over"; and now, having paid more attention to something Mr. Phillips said in the below post:
Traditionally you wouldn't want to let car wash soap dry on your car's paint as it would look like a film on the paint.
I would encourage you to substitute my generic usage of:"surfactant-liquid"...To:
'Baby Shampoo'...Especially one of the: "No More Tears" variety.
-
But, surely, there must be more money-savvy ventures than: Homebrewed Detail Sprays...:dunno:
Bob