I think cohost keeps hidden for privacy reason. Finding people in cohost is definitely hard. Best ways are connecting to people you know elsewhere, looking through tags and stumbing on people who post-good, or reblogs, but first you have to find someone who reblogs good stuff through methods 1 or 2.
Also on more generally on the topic, Cohost is definitely not a twitter replacement, or alternative. Form wise it more closely resembles tumblr, but it’s not really that ether.