That video made me cringe. Very few "maintenance" videos are really good. - this one is marginal.
One does not need to drain the rear just to check/lube the splines. When you remove the sensor just take one of those yellow earplugs and stuff the hole just enough to plug it - do not shove it in so far you can't pull it out.
Don't use your foot to support the rear-drive, use a jack or similar. It's heavy and it's not loose until it's loose.
Have a tie-strap/wire/coat hanger/etc. ready to hold the rear brake when it's unbolted so it's not flopping around while you're trying to figure out what to do.
There's a reason a ratchet has a handle, it's a lever and provides a mechanical advantage.
Work smarter, not harder. Be as professional as you can with what you have.
If you've gone through the effort to open up the rear-end to get to the those splines... guess what... open up the front end, it has a splined shaft & u-joint in there too & it's not that much more work.
As for a magnet strong enough to degauss your entire bike... I don't think I'd like to "gather" ANY metal(s) out of my final drive. If you feel you have too much on the stock magnet, maybe something bigger is going on and it should be checked.
On one-hand it's nice that information is easy to come by, but the plethora of misinformed & ill guided instructional videos just promotes bad habits and at worst, can hurt you or causes damage to what you're working on.
Anyway, YMMV.
