The rescue diver course is really there to provide you the foundation to be a lay rescuer - that is, you are not a professional rescuer. You have the knowledge to be familiar with a rescue should you ever be in the position to rescue your buddy or someone else, i.e., you've seen something like that before, and hopefully that will be enough to help you do more than sit there.
That said, it is valuable to practice some of these skills. A lot has to do with recognizing problems early on - an ounce of prevention is worth a pound of cure. Think through what a stressed diver looks like - start routinely checking your dive buddies to make sure they aren't wide-eyed and hyperventilating. As you are diving, think through random failures and how you would solve them. Start being stricter with yourself and your buddies about fundamental skills (buoyancy control, trim, streamlining, gear placement, etc). Good fundamental skills prevents a lot of problems.
If you want more actual scenario practice, find some buddies (who already have their rescue cert), hire an instructor, and ask them to just spend a day refreshing rescues. The reason for an instructor is that they'll be better able to spot problems, instead of you all trying to remember nuances. The instructor (especially if they're attached to a dive shop) will also (hopefully) have access to additional equipment (like a float to attach ditched gear to, donor bp/w for cutting off of a patient, CPR dummies, etc), and already has realistic training scenarios planned.
Finally, keep your medical skills up to snuff. Your O2 provider does expire, so make sure you recert that. Go take a Wilderness First Aid course to broaden your skills (really focus on the patient assessment drills - that's the money).
One note about scenarios - you need to really think them through in terms of how realistic they are and what the training value is. Scenarios are training value for both rescuer and patient/actor - rescuer needs to use their skills and knowledge to solve them problem, while the patient/actor needs to use their knowledge of what is going wrong and what is happening to evolve the scenario and make the training realistic. Just having your friend act unpredictably underwater isn't helpful - they need to know when and how to respond to the actions that the rescuer takes. It is even more valuable if the patient/actor reacts negatively to mistakes that the rescuer makes, instead of allowing the rescuer to simply gloss over that mistake. There are also a lot of different scenarios to look at. Just a few I can think of immediately - OOG diver, unconcious diver, failed wing, cramping, shore carry w/ unconcious diver, boat entry w/ unconcious diver, drysuit diver, rebreather diver
