DO NOT DISASSEMBLE THE SHOCK WITHOUT COMPRESSING THE SPRING
The following only really applies to automotive shocks. Moped shocks are generally sealed and non-rebuildable.
If you take apart a shock without keeping it compressed, you will probably be seriously hurt from the impact of the shock exploding. There’s such a big force behind it that it will rip apart anything it hits.
Go to any automotive store and spend a very small amount of money to get something much safer:
(Spring Compressor pictured for automotive shocks)
Tighten the bolts (use an air driver or an electric drill for convenience) until the spring is compressed far enough to release the holding nut on it. Release the nut on the shock itself and then slowly undo the nuts on the holding device.
You’ve now successfully taken your shock apart. Putting it back together is the other way around.
And about painting it: You’ll need a flexible paint for your springs if you want to paint them too. The metal flexes a lot, and regular paint can’t stand that that well. A good paint is RC-car paint, as this is designed to be able to flex with the body of the cars.