IF this is your acoustic, what type of finish is on it? urethane? shellac, epoxy? here is a good article abut what will work with what, http://www.diynetwork.com/home-improvem … index.html
but I honestly thing you can use whatever you want. If you look at the chordi stock pics Chick has a hand painted guitar that looks like craft paint or acrylics with a clear coat over it. If your going the stencil rout, or complete change rt my favorite all around durable paint is Auto paint. Duplicolor has tons of options and large and small cans even touch up colors if you only need a little bit of a color, and then clear coat it a few times to protect what ever art you have. Remember after you have put all the work into the design,, you do want to protect it. The more thin layers of C/C the more protection and also more sacrificial layers so you can wet sand it to a deep gloss. 1500 to 2000, to 3000, then some quality rubbing compound (and a easy one that is very good and off the shelf at wall mart or an auto store is Meguiars Ultimate compound ) and polish (Meguiars Ultimate Polish) followed by a good sealer or wax. and your ax will look fantastic. I have only scratched the surface here, PM me if you need any more help.
I know your talking an acoustic, but paint is paint.most guitars you see with a solid finish and artwork is clear coated any way. like say this one
“Find your own sound. Dont be a second rateYngwie Malmsteen be a first rate you”
– George Lynch 2013 (Dokken, Lynchmob, KXM, Tooth & Nail etc....)