would it work if you used one of those ronseal tubs what you spray your fences with work the same way if you wanted to spray parts of your car?

I'd say that's a fairly strong no.

Well, it MIGHT spray the paint around, but the chance of getting an acceptable finish is nil!

The fence paint stuff is much thicker than car paint, and the nozzle will give a much larger droplet size.

i thought so.. but also thought could be a small chance

Try it! Let us know the outcome