He pushes the front leg down and steps over in an attempt to pass
You counter with reverse de la Riva and recover de la Riva
Sweep him onto his hip and berimbolo to the back
Correct use of the seat belt grip from the back to secure the cross collar grips
Change up from the cross collar choke to triangle from the back and finish
Pull de la Riva guard
Gui prefers to pull guard and control the ankle because it restricts your opponent's ability to move from side to side. Restricting side to side movement makes passing the guard much harder.
Grab his R sleeve with your L and his collar with your R. R foot goes to the hip as you sit, wrap your L leg around his R in a de la Riva hook, and grab his R ankle with your L hand. Grab the ankle not the pants, so that you do not have to lock the grip on constantly and burn it out.
Your R hand should grab his R collar (cross grip). Edit: It may make sense to start the guard pull with the R grip on his L collar (parallel grip to stop him getting your back while standing) and then switch to the R/cross collar during or immediately after the guard pull. R foot goes to his hip, knee, or bicep.
He will attempt to pass by pushing your R leg down and stepping over it, perhaps then moving to a cross knee pass.
Counter the leg push and step over
Your grips on his ankle and collar do not change.
Your R hook now goes behind his L thigh for the reverse de la Riva hook. Ball up and roll backwards onto your shoulders, using the R hook to in effect throw him over your R shoulder. Edit: Use everything you can to knock him over - ball up and use your back, the momentum of the roll, quads, everything you can in your anterior chain. (Next morning) I have a slightly pulled muscle in my thigh or hip flexor which I feel resulted from trying to do this with too much hip flexor and thigh and not enough of the rest. He should at least post on the floor with both hands. Spin back and re-establish the regular de la Riva guard. Your R foot can go to his L bicep, or ...
Sweep his onto his R hip
Re-establish your de la Riva guard as above, but now roll back to your left, escape your hips to the R, put your R foot on his R hip and knock him over onto his butt and R hip. Edit: The transitions should be explosive. The rest, not so much.
Berimbolo to the back
Invert from here ....
This video goes into the details of the berimbolo as the Mendes brothers perform it far better than I could in words. The only major difference to what we did at the seminar is that he grabs the belt rather than the collar (and the video features Rafa, not Gui). But the differences otherwise are pretty minimal. And you can see how close the collar is to the belt at the beginning of the technique.
Main points I got from today is to pull down hard on the collar to keep him close, do not release the grips except when you need to near the end, try and keep your chest close to him when you finish the roll, and after you have changed your grip from his R to his L ankle, to keep that grip and jam your L hook into the back of his L leg so he can neither turn back toward you or get away. Then you can establish your seat belt grip and back control.
Seat belt grip from the back
Gui likes to grab the open hand of the arm around the neck with the hand that goes under the arm on top. So, if you have the seat belt grip with your L arm over his L shoulder and your R arm under his R armpit, you should grip the blade of your L hand with your R. He will try to pry off the top hand, your R, with his hands, and when he does the L hand is free to choke, either rear naked or grabbing the collar.
Gui will use that grip to get his L thumb inside the guy's R lapel, so that when he peels off the R hand your L hand can zip straight up his R lapel to his neck, ready to choke.
Cross collar choke, switch to the triangle to the back
You have the grips for the cross collar choke from the back. Assume The L hand is over the shoulder with the thumb in the R collar, the R arm under his R armpit gripping his L collar. Stay tight. You could choke from here.
Put your L foot on his hip. Then use it to overhook his L arm. Post your L hand on the floor. Put your R foot on the floor and escape your hips to your R, grab your L ankle with your R hand and slide the crook of your R knee up to his neck and pull the L foot up near his R armpit. Triangle off the L foot with the back of your R knee and hide your R foot next to his R hip.
Finish by grabbing his R elbow and lying back, pulling the elbow as if performing an armbar to crank his shoulder. You can also do a wristlock on his R hand, or reach for his R leg and pull back for a legbar. This video is not exactly the same technique but is quite similar and shows the elbow pull finish:
Drills and exercises
Gui encouraged us to do plenty of drilling in guard retention, e.g. trying to retain and recover a particular guard for a minute at a time while your partner tries to pass. Just retain the guard, no sweeps or submissions. Gradually increase the time.
Confidence with your guard will make you strong and confident at Jiu jitsu.
We also did a drill where you have your partner's back with the seat belt grip. No hooks. He rolls, hip escapes, etc, and tries to get out for a minute while you try to keep him there. You can use hooks behind his thighs but not in front. After a minute, swap places with your partner. Do several rounds.
Gui also encouraged us to practice moving around, side to side, etc. in as low a stance as possible, butt next to our heels, so as to leave no space for passing and to practice balance.