That method means the line from the caliper to the slave cylinder is pressurized. It can pop off spraying fluid everywhere. I've tried the pressure canister as well and have had it work. I also have had the hose pop off using that method. For me it just took forever and was kind of a pain. this is done with one nipple connection, and a no pressure line. It takes 15 minutes, 10 if you have a helper pump the clutch and fill the reservoir.
If the normal way is easy for you and you have it mastered then that is the way to go. I have a hassle trying it that way every time, and will never go back.

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Chris
84 280sl
82 300d euro