@(you need an account to see links) has two really excellent guides, the "what is a cache" guide that i see that you have already read and have questions on, and the answers to that are in her other guide about (you need an account to see links) just putting a pet on a shell and caching the pet isnt enough if you are going to trade it on the PC. you need to make the shell look... not like a shell, like it would actually own the UC and be interested in trading it. additionally, i would not advertise it as UFT, but neomail your offer on pets you see UFT instead.
stay safe! don't go flaunting around your shiny new toy. here are some more guides:
(you need an account to see links)
(you need an account to see links)
(you need an account to see links)
(you need an account to see links)
all right here in the guide section, you just needed to look. c: