To use this trick you first need to create a track that will serve as a customized metronome synced to the tempo of the song. I know, it sounds complicated, but trust me, it isn't! You only need a virtual drum plug-in ─ don't worry about its quality, it won't make any difference in this case ─ playing a note on every quarter note (make sure to quantize it so it's exactly on the beat). Which note it is doesn't matter either, since you are not going to listen to the drums solo anyway. Now, modify the routing of the track so that it doesn't go to the master bus.
The next thing you need is a pink noise generator. If your DAW doesn't have one, you might want to try the free MNoiseGenerator plug-in by MeldaProduction. Insert the noise generator into a new track, add a noise gate with external sidechain and feed the latter with the metronome track you just created. Dial in the gate like this: Range set to maximum, attack and release time set to minimum and the threshold set low enough so that every beat of the metronome opens the gate. Once that's done, you only need to send the gated pink noise track to the reverb bus.
And then what, you ask? Well, you should hear the pink noise nicely soaked in reverb appear and disappear in tempo with the song, And what's the point of that? Quite simply to be able to distinguish the color of the different presets of your reverb. In fact, pink noise is the noise that best adapts to the logarithmic perception of the human ear. Hence, the hide-and-seek game created by the combination of the metronome and pink noise is an excellent way to expose the tonal characteristics of a reverb. So, toggling between presets, you ought to be able to quickly identify which preset matches better the emotional aspects of the song in question.
Besides, this isn't the only use of this nifty trick. The metronome/pink noise combination you just created will also allow you to fine tune your reverb settings afterwards. But that's something we'll come back to later on...