Is anyone else still shiny hunting Zygarde? Any advanced tips?

I have been hunting Zygarde for a while now, playing with NPCs.

I know how Wide Guard is a must, along with an Ice type to deal damage.

My strategy has been to keep playing through until I find a good run, which has a combination of Wide Guard and at least 1 ice type. I would spam Wide Guard while the NPCs would (hopefully) use Ice moves. Then I would quit the game after confirming the Zygarde is not shiny, but before the game saves. Rinse and repeat... with roughly a 75% success rate.

But having to pay 10 Dynite per attempt killed the strategy. I ran out quickly, and I only got 200 after multiple hours of playing.

Now my plan is to keep playing through until I find the near-perfect run with Wide Guard and multiple or high damaging ice types... a run where I get a 90% success rate.

What has been your most efficient strategy? What's the quickest way to get more Dynite?

Are there groups of people hunting together? I don't know how multiplayer works in terms of hosting... how do you guarantee a good run of available Pokemon everytime in multiplayer?