Generally I find super glue and canopies to be bad news, as they usually fog due to the fumes. I used to use Johnson’s Klear to fix them in place but it’s hard to get now.
Good old PVA is used by a lot of people, but I’ve recently discovered a clear drying glue called mig ultra – good results so far – it’s strong, dries clear and if you use too much can easily be cleaned up with water.
As for the airbrush, well if you can afford it, it will be the single biggest thing you can do to improve your results, but it does take a bit of practice, mainly knowing how to get different types of paint to the right consistency. Also budget for a decent compressor though!