Seems like this post is slowly dying out, but I think I've got part of it... Maybe. I'm no pro at this, so I could very well be wrong.
With the discussion on the slow-mo thing and how many mobs/mooks to kill during/after, I don't know if it matters. I've done it 4(?) times now, two on the first day by accident, twice on purpose. My third time was my first attempt for the day, too. The thing is - I never match up how many I kill on the killing blow. There was discussion a while ago on 3, but I killed 2 or 3 the one time then 8 the next, and it still worked. Same thing with the number afterwards. I've done 1 and then up to 10. As long as the rupee count doesn't go over, I don't think it matters.
The overflow thing above talks about that being the glitch, where it subtracts the 100, which then causes it to max out. If it's not readily accepted, I'm 90% certain that's the thing. What I think is the deciding factor is to get a mob and the boss to "explode" at the same exact time, which is what makes it not an easily accomplished thing, and why some people make it happen often and some don't - some have a more natural rhythm to their play, probably. I know that sounds like a cop-out, but I'm fairly certain that's what it is. Each time I've had it done, if it's slow-mo, I wait literally a beat then dodge into weak attack on mooks. One time I did a spin attack (success 2, I think).
This is what leads to the calculation fails - not attempts where you are off, but where the RNG and calculator isn't on your side. You get those amounts of rupees instantly added (100, 450, 500, etc.) Sometimes that pops up instantly instead of the -100, which is (likely) what causes the glitch. If that happens, the timing was correct (I believe), but it went positive instead of negative.
I think these two factors - timing and the calculation - is what makes the glitch so hard to replicate. Some attacks/animations may be better/easier than others (ie the summoning gate vs, my attempts with Link's sword, the only weapon I've tried), which is why there may be varying levels of success as well.