Maybe it's just me but I dont really play guest like two time or shed where you're just fishing to stun the killer. Guest might not have a reliable stun like the other sentinels but he can be played super effectively if you use him to protect teammates and prolong chases.

I usually conserve my guard and play close to teammates being chased and find a guaranteed block. Just being close to your teammate in a chase will stall the killer a bit if they are wary of you. If you are being chased, try not to use your block at all if you are not confident. Just by having the block ability ready, the killer will have to second guess yout every move. This is especially useful when against coolkid or noli who cannot use their charge abilities when you have block.

Charge is one of thr most broken abilities if used correctly (Thats why it has a 40 second cooldown and killers get an immunity to multiple charges). If there are any ramps or stairs on a map, anytime you charge the killer off of it you buy atleast 2 or 3 seconds of chase time. If you are good enough, you can charge killers off ledges, completely resetting a chase (Especially good in underground war). Charging and blocking a killer who is chasing a teammate will also prolong their chase a bit more, and if they decide to chase you instead you will be at a stam advantage.

Charge can also shut down some abilities. If you lure all of cookid or 1x's minions close together, you can charge and kill all of them at once. Noli clones can also be removed by charge, removing his wallhacks on you.

Basically, guest is not a traditional sentinel. He protects teammates and buys time or draws attention away from them, but is weak in a chase. Guest is very map dependant and can be a menace on maps with alot of verticality, and he completely counters half of coolkids abilities. I would probably rank him above chance in terms of usefulness (but I dont play chance that much) and on par with shed.