Following it and Holding it are two different things. You don't need to click on a talkgroup to listen (unless your priority setting for it is low), you click the Priority Field to Hold it.
There is no quick way to Hold two radios in a private call. You could make the Threshold very high (low number) then change the radios to a priority higher (lower number) than the threshold. By the time you do that, the call will be over.