Killercurt,
IMHO: Using the airbrush proficiently is going to take practice. Then more practice. Then more practice. The uber testor paint should be ok, but likely needs thinning. If you’re not already, you probably should be thinning your paint. Try to use thinner specifically for your brand of paint, eg. Testors airbrush thinner for testors and modelmaster paints, and of course use acrylic thinner for acrylic paint, enamel for enamel. I generally use a ratio of 9:1 paint to thinner, I use only acrylic flats. As far as practice use a cardboard box as your practice canvas. Experiment with distance from the painted surface, needle adjustment for paint flow, trigger pull, thinning ratio, air pressure. It wouldn’t be unreasonable to try some exercises eg. Painting large areas, lines, shapes, before even hitting a model. Remember to keep the airbrush moving constantly, whether it be side to side and/or near and far. As far as the can regulator it’s been many years since I’ve used compressed air cans, and honestly can’t remember. I use a compressor and would never go back to compressed air. You can get a reasonable badger compressor at your local Micheal’s, be sure to use a 40% off coupon. It’s like broadband vs. dial-up, a whole new world opens up. If you do get a compressor I recommend getting an inline water trap. You can get an inline air regulator for $6-7 dollars at your locally hardware store, for greater versatility. Finescale.com has an online article at http://www.finescale.com/fsm/objects/pdf/abcsofairbrushing.pdf which looks pretty good. Addtionally the Dec 2004 printed issue had a great article on airbrush trouble shooting. Of course you want to have a clean dry model (I use hand dishwashing detergent, and a soft toothbrush) free of dust, and finger oils. You’ll want to paint is layers or coats, not trying to get everything done at once. Your results will be much better with multiple light coats vs. few thick ones. If you build models you likely already know, patience is key.
Also, if you would be more specific, specifically what problems did you have? Paint running? Water coming through, paint buildup? We might be able to get you some better info. Good luck, and did I mention practice! Hope this helps.
AF