Pokemon Go How to Get Shadow Shards Faster?

The main topic in the Pokemon Go community is the newest feature, Shadow Shards. These mysterious objects help immensely with the severely powerful Shadow Raid Bosses, but the big question is: how to get these Shadow Shards faster?
An interesting theory (if I can say that) has appeared on YouTube, where the user going by the name Poke AK first explains that Shadow Shards can be obtained through One-Star Raids (one Shadow Shard per One-Star Raid) and through defeating a Team Go Rocket Grunt/Balloon/Leader (three Shadow Shards). Defeating Giovanni, the Boss himself, will give you four Shadow Shards. If you gather four Shadow Shards, you can turn them into a Purified Gem, which is much needed when going up against a Shadow Raid Boss.
How to get them the fastest? Poke AK says that to get Shadow Shards much faster is if you engage in a few Team Go Rocket battles. These battles give out the most Shadow Shards, and the more you have them (Shadow Shards), the more Purified Gems you have. You can also combine Shadow Raids with Team Go Rocket battles, and you will collect even more Shadow Shards. The good thing is that Team Go Rocket Grunts, Balloons and Leaders are everywhere. Literally everywhere, giving you multiple chances to battle with them. It’s quite an interesting (and successful) theory if I do say so myself.
Poke AK’s advice to you all is to stack up on Shadow Shards and Purified Gems before the beast arrives, and that beast is Shadow Mewtwo. We all know how difficult this Pokemon is when it comes to defeating it.
Have you gotten a Shadow Shard? How many do you own at the moment?
I love you Pokemon go