>>58739987I'd say the dlc is better than any dlc they've made before, the process is simple, you make a donut with berries, that donut will have random powers, including alpha power,teensy power, sparkling power etc, like the S/V sandwiches, and then there's portals all over the map, you choose a portal and proceed to fast travel/teleport to reset the pokemon and get shinies really fast.
There's a time limit in those portals but you can just reset if you don't get what you want, plus while fast traveling the timer goes by really slow.
I'd suggest watching a video guide
As for grinding the base game, I don't see the point, the dlc builds upon the base game so you can just do both at the same time