In short,
High dose prednisone 60-100 mg a day for 2-4 weeks can help especially in an episodic situation while other modalities kick in. It can also help with getting some sleep if one gets strung out on nocturnal attacks. Many docs prescribe a dose pack which is a burst dose with quick taper commonly used for back pain. This may have short term help but its not enough for cluster headache in most cases.
Of course there are costs with the benefits. Prolonged steroid use can suppress the adrenal glands and it might be a struggle to get them back in sync. The more feared side effect is aseptic necrosis of the hip. This is a situation where the blood supply to the hip joint is occluded with small fat emboli and the bone dies and the joint needs replacement. Unfortunately this situation is not dose dependent and unpredictable when it might occur. On the flip side many many folks need steroids for a variety of conditions and tolerate them just fine. Long term steroid use can cause other issues so its not practical in our situation.
The most common side effect is agitation and short temper especially during withdrawal.