Essentially the same way as one teaches their daughters to remove the Lug Nuts on a car.......when teaching them how to change a car's tire.
Well, as you know the lug nuts on a car's wheel are typically tightened with an air-impact wrench when new tires are installed or when the tires are rotated....etc...
Heck, it can be a serious fight sometimes for a strong young man if they are simply just using their arm strength with the Lug Wrench(tire tool..)
....Well how an old person can do it , and how to teach a 16 year old daughter to easily do it......IS TO USE YOUR LEG POWER and stand-on the end of the car's lug wrench....................don't necessarily karate kick it like cranking an old motorcycle ...DON'T because if you kick it wrong....you can send the Wrench flying off and it can hit the car denting it, or could hit you or somebody nearby....not good...right.......thats why............................giving it the ol Chuck Norris kick will work, possibly faster, but with serious potential risk of flying wrench impact damage to you or somebody near you or something nearby.
Obviously, the longest handle wrench that you have that FITS the bike pedals will give you the greatest leverage, but you absolutely need the correct size or an adjustable Crescent Wrench that is also narrow enough to work. YOU DO NOT NEED A QUALITY WRENCH FOR BIKE PEDAL REMOVAL & INSTALLATION. Any el-cheapo Chinese steel wrench from the likes of Harbor Freight, Family Dollar, Dollar General, Auto Zone, O'Reillys, Advance Auto, Northern Tool, WALMART, Lowes, Home Depot, Tractor Supply, Ace Hardware, NAPA, Target, Kroger, or anywhere else that you can buy very inexpensive cheap wrenches & or adjustable small Crescent wrench. You don't need quality tools like Snap-On or old style Sears CRAFTSMAN, etc... You're not gonna use them enough to wear them out or break them , during the next thirty years..............yeah, they will rust and the horrible chrome plating will deteriorate but they will function decades from now. If you're a professional plumber or mechanical contractor/HVAC technician or Auto mechanic/SAE certified auto technician, then you'd need quality tools because they use them so often and their physical shape/contour matters as something as minor as shaping makes it easier/faster to work in tight spaces and makes for a better human hand grip and better comfort for the person's hand and arm. Time is money and speed and comfort are huge in the professional trades..............also tool breakage or/and marring/ruining a bolt head or nut or the fastener/part itself is a huge deal as it causes a major delay when that occurs...............also if nothing else and nothing breaks or ever goes wrong, just having more comfortable ( ergonomic) tools allows the professional to do the job slightly faster.........yeah maybe only minutes faster but over the period of a month, or a quarter, or a year's time, it does make a difference in profit and the best quality tools more than pay for themselves..................but for the average homeowner, one just really does not need fancy brand name quality wrenches............even if a minor hobbyist with old cars, old motorcycles, and old bicycles.
The $1 or so cheapie chrome steel china made wrench from the likes of Harbor Freight store, or direct from some ShenZhen based massive Chinese seller on e-bay is not gonna be any worse than the most expensive tool, as long as it is the size that fits. That $1 cheapie wrench will not last as long as a quality tool, but you aren't gonna do three thousand bicycles and other project uses with it during the next five years. You'll more than get your money's worth on the cheapie.
Another thing, don't worry about the cheapie tool.......for example, suppose that you need more LEVERAGE......you could if you have a suitable piece of scrap galvanized steel pipe or other steel pipe............place the pipe over the end of the wrench as an extender bar................you might have to fill space with something like inner tube wrap or duct tape etc to make the pipe fit the wrench snuggly enough..........................hey you can also bang/hit the end of a cheapie wrench to get certain jobs done...who the heck cares if the cheap wrench gets mucked up, as long as you accomplish your task.........so you modify or ruin a cheapie wrench............BFD (big f-en deal) as it only cost you a couple of bucks. MacGyver (the real one as played by Richard Dean Anderson) would likely approve! Remember that if things look really RUSTY & frozen with huge amounts of rust....you could try letting some Penetrating Oil attack it for a few days before trying to loosen it.