For Cobalion's "Follow-Up" attack, can I choose a Benched Pokemon, search for a basic Energy card and attach it, and then choose my second Benched Pokemon and search my deck for a basic Energy card to attach to it?
No, you need to choose both (or choose only one) of your Benched Pokemon first before making any searches of your deck.
Source: Silver Tempest FAQ; TPCi Rules Team (2022-11-10)