Hey mate, if you paint the guitar in oil paints you wont be able to use any other product other than an oil based clear coat which i dont think exist.
Depending on what oil paints you are talking about, if they are arts and crafts paint see if a crafts shop has a can of oil paint sealer.
If it's not that type dont use it and just go with 2pak or acrylic.
If the guitar is in 2pak you can use 2pak clear or risk using acrylic clear but i wouldn't attempt it on first go.
if the guitar is in acrylic then you can only use an acrylic clear coat.
I'd assume its the same for nitro finish.
It's not hard to paint if you want to do a basic solid color or layered finish if you can be creative with stencils.
You tube some spraying videos, even car painting will help. You can do some kick ass stuff with 2pak spray cans.
Gimme a buzz if you need info on what stuff to use. I used to be a back yard sprayer.
