Yeah my facelift rusts like you wouldn't believe, think vx counted the plastic and glass when they quoted 75% galvanised panels on the facelift.
Anyway, I've got some experience in dealing with this issue. You need to remove the rust completely otherwise it will come back.
The only way to remove rust is to use a sandblaster on the source. Made many mistakes using a grinder and wire brush attachment to remove rust. Came back after 6 months. You need to get your area back to bare metal.
Then feather the area around your bare metal then apply primer to build up layers, etc, then apply base colour and then lacquer, etc. etc.
VX touch up kits is really thick and I mean like tar thick. Haven't tried them with my airbrush yet but I guess it needs to be thinned out.
If you are going to try this yourself do research on painting your car and do some practice. The key is to take your time.
Another tip which no one told me, was when you apply a pearl or metallic colour coat you don't need to rub it down before you apply the lacquer layer. You apply the lacquer on top of the colour coat and give a good layer of lacquer, and then you can use very fine sand paper to smooth out any imperfections on the lacquer and blend in with the surrounding paint.
There are loads more steps involved, this is just a rough guide.