What has been described, is industry-standard across the board. That's how it's done.
The booster battery might be needed only if your stock battery isn't very strong or isn't fully charged. Spinning the engine over with compression only on one cylinder doesn't take a lot of effort and isn't particularly demanding on the battery.
edit: Kawasaki recommends to do this with the engine warmed up. There are two problems with that. #1, if you are trying to diagnose why an engine won't run, you can't warm it up, because it won't run. #2, on the particular bike that I am looking up the service manual for, it takes 3 HOURS to gain access to the spark plugs! You might have started off with a warmed up engine, but by the time you finish stripping down the bike enough to gain access to the spark plugs, it won't be ... The R6 is no picnic for getting to the spark plugs, either ...