Sure, it can be done easily. As you say, all you need is a high contrast object to focus on and take a couple of shots. Better yet, any former RPG junkies (aka D&D nerds ), you probably still have one of those 20-sided dice, so roll a d6 with 1-3 being negative and 4-6 being positive, and the AFMA value from the d20.
Of course, there's doing an AFMA, but then there's doing it correctly...
Seriously, there's a reason Canon sort of discourages doing it in the manual, warning that it may prevent you from achieving proper focus. AF systems are neither perfectly precise nor perfectly accurate - multiple shots are required, the target must be appropriate, flat where the AF point is (the whole real one, not smaller-than-real little box in the VF), etc. I really recommend using FoCal or a commercial tool like LensAlign or SpyderLensCal, and take lots of shots.
They also recommend doing in the field too .
Honestly aiming at a pavement crack gets you 99% of the way there and same goes for picking some player standing around and taking some shots and checking at 100% view. People do it one the sidelines. You can tune it to typical distance being shot at at the time. Once had a 5D2 and 50D and 300 2.8 and a TC, before doing some quick MFA on the field I was getting like 1 in 6 shots with good focus, a total mess, a quick tune and sudden;y using the TC was viable for the soccer match.
Another nice reason for MFA, what if you end up using pool equipment from a newspaper? You are not in control over when/if/how it gets calibrated. And if you grab a lens maybe you do need to do a quick MFA on the field of play. (And speaking of Rebels again, lots of students use them and many school papers have pool lenses so you can see Rebel users could surely make use of MFA.)
Don't aim it at some ruler 1' away from you that is way too close for one and gives it too many things to grab on for another.