Painting guitars are very tricky. You have to treat them completely different than anything else when it comes to painting, so you will not change the sound or feel of the guitar.
First try not to take off the stock finish or expose any bare wood if possible. You can prep it two ways or a combination of both. Start by sanding it with a DA with 220 grit at a very low speed. Block sand with 400 grit wet/dry and use a red 3M scuff pad to get around all the corners and edges. Before you go any further you need to set it up so you won't change the sound or get any cracking due to moisture (especially if you wet sand. Tape off the inside of the routed pick- up areas with duct tape (this will keep water and paint from the bare wood.); Fill all the screw holes and any open electrical channels. I use Play Dough; it doesn't bond to the wood and is easily removed. If you don't do this step and any moisture gets in the open holes, the wood will eventually split and crack the paint. If it has a bolt on neck, tape off the area where the body and neck come together (if you don't do this it will change the action of the guitar. If you need to fix and dents or cracks use a fiberglass filler (Evercoat). If there is any extreme damage, route a groove and fill it with fiberglass matte. I've actually repaired guitars that were split in half. The wood absorbs the fiberglass resin and gives a strong bond.
You can use either a polyester or epoxy primer. I prefer the epoxy primer/sealer (PPG DP-48LF). Let it dry 24 hours then block sand it with 400 grit wet/dry sandpaper. This is where it's really important to have the holes filled. If you're not familiar with painting the DP-48 primer needs to be reopened after 24 hours so the basecoat will bond.
Now you're ready for paint and graphics. I prefer the PPG DBC system and House of Kolors basecoat. I'm not sure of your painting experience so I'll do a quick run down of the finishing procedure. I shoot all my graphics and illustrations first, and then clear coat (4 coats), then color sand with 400 grit (this levels the graphics) and then I do all the detail work and striping. Clear coat again. At this point you can color sand (1500 grit then 2000 grit) and buff. I prefer to let the guitar sit for a week (even though the guitar was sealed, the wood tends to absorb the material for several days and you stand the chance of the final finish shrinking back if you start buffing too soon.), wet sand again with 400 grit and clear a third time before the final color sand and buff. I've found it best to use 3M foam pads with 3M Perfect-It 2 Micro Finish Compound and 3M Perfect-It 2 Foam Pad Polish. If you use a wool pad you WILL burn the finish. The reason for this is the wood heats up when you buff and causes the clear to shrink with it. This is the only way I've found to give the guitar a primo glass finish.
By Steven of SKC's Cutting Edge Designs
Hey, I've got a question for all you fellow paint sniffers...When clear-coating a guitar, what's the best way to hang it? I've strung a coat hanger through the holes where the neck bolts on, but when I shoot the paint on, the blast of air pressure from my spray gun causes the guitar to swing back and forth and makes it really hard to get even coverage. Holding the guitar at the base of the hanger helps keep it steady, but then I get a blast of paint all over my arm, and while I'd like to have smooth, shiny skin, this is not what I had in mind! If any of you have found a better way to hang a guitar please let me know... Thanks!-Daneen
Hi Daneen, I needed a little more info to see where you problem might be. I'll just run down what I find to work best. First of all, I have a chain that clips from one side of the booth to the other. I use wire from a wire fed welder. Its thinner than a clothes hanger so you get better coverage with the clear behind the wire. On a bolt on neck body, I run a wire through on of the neck holes to the chain and loop another one through the hole for the power/amp cord. This wire is ridged enough to shape it so it stays away from the body.
I don't know what spray gun your using. The one I found best for clearing guitars is the Sata NR 2000 HVLP. It actually needs less air at the tip than any of the others. It only needs 24lbs at the gun for clear which in turn doesn't push enough air to make the guitar move around.
Hope this helps you a little. Steve