Well, it seemed like the OP was interested in aesthetic modifications to the controller, and those are really simple to do. All of the buttons in a controller simply slide out, making them easy to replace with different ones. LEDs in the buttons are a bit more complicated and require simple knowledge of soldering, nothing too complex though. In terms of actual improvements that would benefit gameplay, you can replace the thumbsticks, d-pad, and possibly triggers (not sure).
In terms of painting, you have three options. You can get spray paint such as Krylon Fusion and paint base colors, or use stencils to get a bit more advanced. Another option would be airbrushing to get high detail and really make a controller pop, but if you don't already have the supplies and know-how, it's not going to be viable. Finally, my personal favorite, is a process called hydro dipping. It's used commercially on things such as gun parts, but most of the big custom controller companies use it for their controllers. In simple terms, hydro dipping is the process of taking a pattern and applying it to a 3D object. It can make controllers look stunning, and it's really a simple process. You can buy kits online and apply them to your controller shells.
I may be able to find an old shell that I painted, and I have plenty of parts if you want a picture of those too. It's pretty late right now, so I'll look for it in the morning.
For those wondering what a hydro dipped controller could look like: www . modjunkiez.com/assets/images/silvaskullshydro1resize.jpg
And for anybody thinking about doing their own: www . mydipkit.com/index.htm
Sorry, I'm not allowed to insert direct links yet, just copy and paste them into a new tab and delete the spaces before and after the dots.
