@KelsonV or by spending rare candy. Maybe with the new #BuddyAdventure it could be worth walking with it again, as it can also increase your buddy's CP.
@FiXato That's what had me finally trying it out - the fact that I can switch buddies without losing candy progress, figured might be worth building up. But it's not clear how long it takes to level up buddy status to get to that CP bonus.