The hardest part is filling the wood grain and making a completely flat surface for your color coat to go on. In your case, Ibanez has done that for you already. So sand the whole guitar uniformly with 320-400 grit sandpaper, and start your new finish. It will adhere just fine. Without that base on there, the wood is like a sponge. Use a sanding block for the top and back so you don't sand any dips in the Ibanez finish, and keep sanding until you don't see any glossy parts anymore.
This is no substitute for reading as much as you can about finishing. Go to projectguitar.com and read all you can about finishing first.
This is no substitute for reading as much as you can about finishing. Go to projectguitar.com and read all you can about finishing first.