@Segatakai Went through sun twice now and I completed both regional dexes for the charm and I've found that, at least for me, the best way is to travel to all the islands and catch all the ones you can catch. The new for game exclusives like drampa for moon and turtanator for sun, just breed something rare with a ditto. Ex: sos weather mons, sos exclusives like chansey, and a mon exclusive to your game. Then post it on the gts, and wait. Obviously this won't work 100% of the time, but it's very helpful for hard mons to catch like goomy. For the ultra beasts and legendaries you can ask someone on this site for help or use your multiple beasts to get the others. Hope this helps 
