Lets see...
- $16 for one can,
- one can will do "3-4 cars" when used correctly,
- the directions caused you to use an entire can and you didn't finish your small car,
- it's a aerosol.
I have used my UQW ($11, 15oz btw) about half a dozen times and I still have 1/2-2/3 of a bottle left at...