atch team renzo gracie guys go for guillotines they tend to finish em.
After seeing Renzo and his guys finish the arm-in guillotine so many times I went back and reevaluated my usage of the technique, and now it works really really well for me. A couple things I revised to make it more effective:
1) Chin grab. Instead of looping the neck right away, I start off from a chin-grip now and then sink the guillotine itself in when I feel the opportunity arise. This reduces the amount of time my opponent has to get his hand into the guillotine grip to defend the choke, and also insures that my initial guillotine grip will be deeper and tighter because I am sinking it when I feel my opponent lift his chin / lower his defenses.
2) Hip movement. I come in from the side of the trapped arm now, instead of falling straight back, and I scoot my hips out to that side as well when finishing the technique.
3) Fast steady pressure. The last key element is that you have to put everything into the choke from the first second that you sink your grip, then maintain that pressure steadily until you get the tap. The longer you spend on the choke the more time your opponent has to dig his chin in, get a hand in on your grip, stack you etc. etc. I find it works best for me when I can apply a lot of pressure quickly and get a panic-tap, or have the choke so deep that my opponent will be out before he can secure effective defenses.
Anyway if you take the time to set it up right so that you get it 100% deep right off the bat and use your hip movement to keep the pressure on their neck rather than the trapped arm you'll find that its a wicked submission.
In honor of Renzo and his team I've begun to call this particular choke the Renzotine when I show it to my class.