what type of touch up paint

[duratalk]

Hi,

I trying to find out what type of paint to use for general touch up, basically for smallish areas from either damage or to repair after rust blisters. Size of areas up to a couple of hand palm sizes, along with scratch repairs.
I have a reasonably decent spray gun, but am not very practiced, and have an air brush touch up gun that works well on tiny areas.
I have tried sraying 2k with mixed success, spraying cellulose (works well in the air brush) and am a dab hand at rollering!
I want to keep the van looking tidy, protect from rust, etc. Van is Blazer Blue.
Any thoughts and tips welcome,

Luke.