To TS, if what you are describing is what i am thinking of:
say you have the head overhooked with your right arm and cant get the guillotine grip, swim your right hand under his left arm and grab a palm to palm grip behind his back (your right upper arm will still be pressing against the back of his neck), pull up on his left shoulder, and he will become very light to turnover (you can use a pendulum motion or butterfly hook to sweep him but he will often be swept over just from the pressure). as you come to mount keep your right hand in his left armpit and arch back while keeping your hips low. Alternatively, you can transition to crosside and control his right arm and sit through for more leverage.
There are other finishes once mounted: eg mounted guillotine, 1 hand guillotine, etc. and if for nothing else its still a nice sweep.