The job procedures are usually the same everywhere, mostly. The materials form the most critical part, and most garages will be tempted to do what they have to do to fill their day. If you can control the materials by purchasing only the best, chances are high you will not face problems later. The price difference between premium materials and others is manageable and worth the final results. Any third-rate material that goes into the process, no matter how minor, will affect the outcome. Unfortunately, the effects become visible some years later.
Even if you give the job to a garage, at least make sure you personally purchase the materials. The people there will inform you the quantities needed of each. The slightest bargain with paint shops gives them a good excuse to rip you off.