If you don't know what OPA is, you should watch this video first.
Also, watch this from 7:20 to 8:34. I use the same letter scheme and orientation shown in the video. My buffer is I, but you can choose any buffer you want. It's just the place where you begin the first cycle.
One more thing...
I was wondering to see what the most popular parity alg is. I did find a thread about this but it was from over a decade ago and I wanted more recent results. Lucas parity is more popular but drew parity is more useful for forcing OLL skips.