This tutorial will take you step by step through the process of painting an ai aircraft using a blank paintkit.
Most ai models from the Aardvark, FAIB, Fruit Stand, FSP or UTT stables all have public pantkits available for download from the usual online libraries.
They typically include a blank basic texture with all the standard details, window and door configurations and so on, so all you have to do is apply the livery you want on that base.
No need for a degree in rocket science to achieve that, but definitely a good dose of patience if you are new to Photoshop.
By the way,I am using Photoshop for my repaints, and all this tutorial shows you how to do a paint using that specific piece of software. Now, if you don't own a version of Photoshop and can't afford -or simply don't want to- invest in it, there are different softs out there such as Gimp, that are freeware, and will probably give you similar results. All use layers and similar if not identical tools and commands, so my tutorial can still be useful using a different paint processor.
On the other hand, if you are an experienced graphic artist -which I am not- chances are that you probably know a lot more about Photoshop than I do, so don't be surprised if I do not use all the shortcuts and functionalities that are probably available. That being said, let's get started!