Are you doing solid color paint or a translucent stain? You will want an HVLP sprayer to do the painting. It is basically the same as painting a car, in fact, I would probably go get the paint and clear coat from an auto paint supply store.
Assuming you are painting it:
As with any and all painting, prep work is 75% of the whole job. You will want to take the neck off, all of the electronics out, bridge off, etc.
Sand the existing finish with 100 grit, then 200 grit, then 400 grit to get the surface ready for paint.
Tack cloth it.
You want a couple coats of color (after it is primed, of course)
After the color, you will want to do multiple coats of clear, sanding in between coats. On your last couple of coats you will want to wetsand with like 1200 grit paper.
If you are staining it, then you just made the project a lot more involved:
If the guitar is currently a solid color, you will want to sand down to bare wood (and before you go through the trouble of doing this, remember that there is a reason why that particular guitar has a solid color paint job. In other words, don't expect to find a flame maple top lurking under the paint
)
If the guitar has a translucent stain on it, you will need to sand the finish off, and then sand the wood down deep enough that you get past where the stain soaked in.
Sand it nice and smooth (200 or 250 grit)
Tack cloth it
Follow the instructions on the can of stain (which you could get at Sherwin-Williams or any other paint store)
Finish the same way you would if you were painting it.
One thing you should note is that the more coats of paint and clear you put on, the more it affects the tone of the instrument. That is why really fancy guitars are stained and then shellacked or lacquered with the fewest number of coats possible. Not like you are that concerned about the tone of a 100 dollar Dean. Good luck and show us before and after pics.
