This has been a real bright spot in my game lately. First, It took me more than a year of constant apllication of the NS choke every chance I got before I started having decent sucess. I tried it on and off for a year before that and never "got it". It wasn't until making the decision that I was going to do it every chance I got, that I started to improve. 0% success at first, then 10%, then 20%, and so on until more than a year later I'm at 50-60%. Now to try and address your question. This is my series of attacks that works for me, and maybe you can try. I try all these in pretty rapid succesion until one hits, very tough to defend one after another without leaving an opening somewhere. Combine these techniques: NS choke, can crusher to darce, Marcelotine. I can't really teach it in this format, so just play with it and pay special attention to where his arm is at and what he is giving you. Also work the knee on belly into the mix.