Way back in the 50s/60s all guitars were coated in nitro-cellulose, this was nasty stuff to spray and wore off over the years. In the seventies came poly coatings, which were much tougher. Relic fetishists like nitro because it's vintage and shows the patina of use, poly coats take a real ding to scratch (although they can develop cloudy patches over decades).
If you want to redo your hot-rod guitar the first thing is to strip it, otherwise you may get paint interactions sooner or later, having said this stripping agents are nasty stuff so may you could spray round the back and see how it holds. The base coat is usually white (yep even when the colour desired is black) and then you build up; Base, colour and several 'lacquer' layers. At each stage you need to wait for proper drying (unless you have a paint oven) which takes weeks and 'cut back' with auto abrasives to make sure each layer is as smooth and flat as possible. It's alot of work so look to do something special if you are going to attempt it, otherwise you may find guitar shops (and even friendly auto spray shops) can do it at a good price compared to all your hours of wet/dry sanding...
'The sound of the city seems to disappear'