Clearly it would be best to wait until warmer weather... but you went with ' warming things up ' and just filling the hole with paint...

I just checked at the local small town O'Reilly's and it has both the ' kit' of this product at $4.50 and the power refill at $3.30. Which negates the need for an air compressor or air brush....

http://www.prevalspraygun.com/home.htm

I assume no one would have a car with just ONE nick which they are going to tackle...

wet and dry sandpaper can be had in single large sheets for ? Even if they are $1 each you would only need three for the whole car full of nicks.. due to the fact that wet and dry used wet will last many many times as long as regular sandpaper....

If your paint is very faded then the addition of a couple of drops of white to your paint may help match the present color.