please excuse me for telling you stuff you probably know, but, if you are having a problem with any process in modelling, have a practice first on some scrap.
i have had similar problems with my airbrushing, so i took myself off to my garage to practice. as in previous posts, thin the paint right down. make sure you are using compatible thinners. paint the edges, inner wheel arches, panel lines, headlamp cut outs and glass apertures first, then concenrate on the panels. thin paint will tend to run away from edges, so coat them first.
if you need to get rid of orage peel, it should be ok to rub it down with wet 2000 grit paper. it should polish up fine.
your model looks good, and you enjoy it. seems good to me.