You cancel a cl.:hp: or cr.:hp: into it for max damage after 3 Knees; also probably the easiest to do. Otherwise you can do the Knee 4 times and then immediately throw out the RJB, timing isn’t that strict thoguh
The timing on the RJB changes depending on the button you use to hit it. L comes out the fastest, then M, then H. It also changes his travel distance, so if you are missing it try a light one. I believe L also does the most damage.