Cortisone shots actually refers to what is known as intralesional steroid injections. It is a fairly effective way to treat persistent modular cystic acne.
The injections are administered by a fine micro needle and the steroid administered can be mixed with some lidocaine to dilute it and lessen the discomfort. It works well because the steroid has a strong anti inflammatory effect thus reducing the size of the cyst as well as the redness. You can expect to see results within 3-5 days although in some cases there may be a small residual cyst . A potential complication would be atrophy of the surrounding skin.
From your photos I believe that some of the lesions are not modular cystic but more like papular pustular acne. Another quick and effective way to treat it would be to use the AGNES radio frequency device which utilises a fine needle to conduct the RF energy to the base of the sebaceous glands to destroy it. Once the glands are destroyed there would be no more excessive sebum to clog up the ducts leading to drying up of the acne . Results can usually be seen in 1 week .
Hope this helps
