Generally, pproblems can be addressed in alternative ways that don't risk scaring the dog. I'm not sure what the behaviour is that needs correcting? Generally these things are used as attempted shortcuts when good management and training -- which take some owner effort -- are more productive.
Air collars are preferable some of the things out there :yikes but I'd personally not use one and I don't know any trainers who recommend them. They always risk creating a fearful or fear-aggressive dog. There are YouTube videos of people trying them and they are pretty darn startling -- not something I'd want to use on a gentle breed like the cavalier.
If you are looking for a trainer I'd only go with someone with a CPDT qualification. Too many people out there calling themselves dog trainers with little real knowledge. You can locate CPDT trainers by location, here:
http://www.ccpdt.org/index.php?option=com_certificants&Itemid=102