I would definitely recommend the "Slaughter bug" if you want the legendary schems from the legendary pals without pulling your hair out or dying from boredom. Once you've beat them once, its easy enough to do again, its the respawn timer that really makes it painful to do legit, but the extremely low drop rate really doesn't help either. It took at least 20 slaughters of each, and Frostallion easily took around 70.
I would say practice the timing on easier to obtain pals first, but the timing is a little bit different based on the size of the Pal and if it's a flying or ground mount. Flying mounts are the easier of the two to time thanks to having a much larger "mount" radius. Generally though, you want to mount the Pal you're slaughtering as the second swing is reaching its lowest point. If you're doing it on a server, you're going to get clipped through the ground then launched into the air when you dismount due to the Pal model bugging out, so be ready to glide. The items from the slaughter will spawn in the air and slowly drift down, so I recommend doing it in an open area where you can easily see all the items when they finally hit the ground. You also want to build a box to dump things into, Jetragon for example drops Pure Quartz, and that shit gets heavy quick even with full weight investment.
Paladius and Necromus also drop Pal Ingots, which can help offset the sheer amount of Legendary Spheres you're gonna run through catching a few extra of each. Necromus specifically drops Large Pal Souls 100% of the time as well, so this is actually an extremely good way to load up on a ton of those. If you do this bug, you're also going to have enough Ancient Civ Crystals to last you a lifetime. Even at 1x, they drop a fuck ton of them.