I would also recommend the DDS/Danaher rotational finish. On most of their no-gi strangles (rear naked, power guillotine, darce, anaconda) they favor a finish where they draw the main choking arm backwards. Same feel as a boanero choke or a one-armed RNC. It draws the arm across the arteries to really cut into them.
@Mikey Triangles was posting about this technique on top-finish, slide-finish, and mount-finish darces way back in 2010. I haven't seen many people emphasize it since then but Danaher and his guys are preaching it heavily on their DVDs and at their seminars whenever they show most arm chokes.
So once you're in the final anaconda finishing position (say with your right arm punched deep while on your right hip) you would clock in towards their hips like usual while also drawing your right elbow backwards slightly. It should cut through most of their resistance and I like it better than what Rafa says to do (mostly just squeeze hard and clock in towards their feet).