I accidentally became a wondertrade pro during gen 6. It's really, really easy.
Go on twitch and time your trades with auslove.
I literally just trade out fodder. Zigzagoon, Spearow, the worst shit.
His fans and mods also send out shinies. Usually great ones.
Whenever I get one with the OT AusLove or
sataki.tv or whatever, I offer it up for trade for whatever offers and take the first one that's better/something I'm interested in.
On a good night, I pulled 3-4 shinies an hour.
I haven't done it a whole lot in Sun. Literally spent about an hour doing it, and I got a shiny Charizard and
Sataki.tv shiny Litten.
Haven't bothered renewing Bank yet, but I plan to in a couple weeks after I get settled from my upcoming move.
I literally have 7 boxes of competition grade shinies sitting on Alpha Sapphire. Pretty much any high tier Mon you can imagine. Literally everything except Thunderus, with random, realistic OTs and great-perfect IVs.
It's the easiest way to collect short of actually hexing them in yourself.