i go to mono mount whenever im in regular mount. recently i changed up my transition a bit because its my favourite way to finish people, i love rubber guard and i love mount so how could i not put the two together... so its pretty sweet.
first ill get a tight overhook on one arm and straighten my other arm out on their same side bicep and put my weight on it so i can move my legs around. then i shoot my overhook side leg out wide so that its straight and my toes are pointing out. if it isnt wide you wont have base while they buck to the sides. once you get there, your basically trying to lift up their overhook side shoulder while pinning their other shoulder to the mat.
once you have them under control, you can try to throw the overhook side leg over their face as if your doing a flying kung fu from the top or you can go to what i can describe as top new york by shooting your leg up to their neck and grabbing your shin and then doing a kung fu move. its important to remember to keep squeezing your knees together in rg even if your on the top, or else theyll buck their shoulders out.
once you get to kung fu from the top, you can transition to mono control by grabbing their free wrist and pushing it away, taking out your free leg so that you can cross your ankles together and then reinserting the free leg back in their underarm.
when i finish the monoplata, i prefer to actually attack the arm with a guillotine grip but with your elbow still basing out, like an overhook armbar almost. i guess you could call it a monotine lol