I only have the basic rulebook and the How do you do that sourcebook, and I'm playing Mage the Ascension 20th Anniversary Edition.
Yesterday I had a player hit with a Life/Correspondence effect that tracked him, and he wished to unweave said effect (and had the required spheres). At the moment I winged it, but later when reviewing the rules I found that I'm not sure how one rolls for unweaving. In the case of countermagic, you simply employ an action, and that's it. But for unweaving it seems, from the rules, that it can't be that simple. The main reason being that it's mentioned the need to get 10-20 successes and a static difficulty of 8 in an Arete roll. I'm aware of the expanded rules in How do you do that, but though they limit the successes needed for temporary effects, wards and so still need more successes than dies an archmage can roll.
So I want to understand how the unweaving mechanic is supposed to work. I can see four options:
You roll once using an action, like regular countermagic. This means unweaving wards or bigger spells is pretty much impossible, which seems unlikely since they are explicitly mentioned as a possible target for unweaving.
You roll as many times as you like, and each time you add your successes until you have enough. This means that given a couple minutes pretty much anyone can unweave anything, since it costs nothing and there is no limit to how many times you roll or any penalties for failure. It seems weird that spells and workings from archmages can be unwoven by complete rookies given a bit of time, and does not really fit with the other things we know from the universe.
You make an extended roll. The problem with this is we have no information on how many times you can roll, which penalties you can get from failure, how much time you need...
You cast a spell. This spell would not follow at all the normal conventions of spells, since it's difficulty would be fixed and independent of it being vulgar or coincidental and it's not clear whether quintessence or tools can be used to reduce said difficulty. While the "begin a ritual" line in the description of unweaving seems to support this interpretation, it still leaves too many of the rules unexplained, and it would have countermagic accruing paradox, which seems counterintuitive.
I can't find any answers in the books I have, or searching the internet. In case they don't exist a house rule, either invented or adapted from previous editions, or an alternative method to get a similar effect would be welcome as an answer.