How to create shortcut to insert specific special character
Two possibilities are through creating a modified keyboard layout (which can be done manually, but is made much simpler using a program like Ukulele) or through a shortcut program like TextExpander

I use TextExpander, myself, so that c== is a shortcut on my system for ⌘, o== for ⌥, and several others, in part because I do not want to lose the symbols already mapped to the option (⌥) key combinations on my keyboard.

On the other hand, remapping the ⌥ keys to symbols different than the ones they are original configured for can be helpful and convenient for some people also, which is where Ukulele shines.