The details John shares here are awesome
In terms of sport JJ (and the RNC being pretty much from a back take): I find it best to be prioritising keeping control and preventing escapes. This means focusing on preventing his head progressing to the mat by controlling his shoulder/arm and hips
When dealing with an experience defender you have to be switching your attacks / controls etc and constantly scooping yourself underneath them until you can get an entry
Broadly speaking you tend to go for chokes from the back by controlling one of his arms with yours & ideally progressing this to controlling with one of your legs
In terms of non-sport training: there are much easier ways to open up the space on the neck to enter in