CS4 is the best tool out there by far, nothing else comes close in terms of power and the ability to get just what you want where you want it.
It may be that it is too powerful for you at your current skill level and you need to learn how to make better use of it. I strongly suggest you do some tutorials (there are literally hundreds on the net if you Google for them) and learn how to use things like layers, the pen tool, clone tool and the various filters. Don't just look for aircraft repainting tutorials either, regular tutorials will teach you how to use the tools and then you can apply that gained knowledge to your repaints.
CS4 is a very complex program and nobody can expect to pick up all of it's features and functions in a day, week or even month! I have been using Photoshop since v1.0 way back in the late 80's and I still haven't used all it's features yet!