Paul, the intent is to systematically eliminate the possibility of an air leak that might have caused the lean condition in the saw. You previously mentioned bad gas but until you determine if/where you have an air leak, it is suspect but unconfirmed. Air leaking past the rings is irrevalent at this point. The objective is to seal the crankcase, pull a vacumn on it and track the time it takes for the vacumn to bleed off. if the saw will not hold -7 psi for approx 10-20 seconds, pressure it up to + 7-10 psi and dunk it. I use this method, as it clearly tells me where the leak is and eliminates the possibility of a false reading of leaks from the plugs or blankoff plates(sheet rubber) behind the carb and muffler(to seal the crankcase). Like cleaning the cylinder, pressure/vac testing can be done different ways. Some people use soapy water in a spray bottle and watch for bubbles around the seals.
If you do not pressure/vac test the saw, and you do have a leak, all your work will be for naught, you will be unable to properly tune the carb(because of excess air) and you will re-score the jug. A search on pressure/vac testing will reveal hundreds of threads which will give you the exact procedure and tools you need. I use a MityVac which will pressure or vac test at the flip of a switch.
Yes, seals can be contentious, especially small ones. They can be frustrating but most can be done with common tools. I got tired of fighting them and splurged on a Stihl seal puller with jaws to fit all Stihl saws(and most other brands) so now pulling seals is very easy. Again, search is your friend and will reveal dozens of homemade and commercial pullers that have been adapted for saws.