Since you can get candy for feeding Pokemon in gyms, I tend to favor feeding Pokemon for which I need candy over feeding my own Pokemon. These are generally Pokemon that I have caught, but haven't yet collected enough candy to evolve. Would this work for Pokemon I haven't caught yet, allowing me to get a jump start on collecting candy to evolve them once I do catch them?
Yes, it is possible to receive candy when feeding berries to Pokémon you do not own. This is commonly referred to as “ghost candy” by users on reddit.
As seen in this reddit thread, a user details how they received candy for Snorlax despite never owning one. After they finally caught their first Snorlax, they had a total of 4 candy (3 non-pinap catch + 1 ghost candy)