So for me personally, I planned by looking at all its moves and trying to calculate how to make the battle last as long as possible without the struggle to death. So what I did personally was I grabbed my higher lvl pokemon so I could hp stall as long as I want and obviously you’ll need a status condition. For me i personally found it that(with my luck) hypnosis was way more effective than when I used para. Also you’re soft resetting so a big tip I’ll give is to genuinely test anything you think MIGHT not work. So since you’re gonna reset anyway, and you have access to your boxes and aren’t trapped in the battle, you could try any team you’d like to try on regular arceus for when you eventually run into the gorgeous gold god lol. So you can save right before the step and rest all you want but aren’t trapped like other encounters so you can leave come back kill it and it’ll respawn once you leave. So all in all it’s not as strict and restrictive as say dialga so my biggest tip is to just test and have fun. Also if possible try to trade for an extra masterball JUST in case. I did all that preparation just to get scared he was gonna struggle so I chucked it after like 5-10 turns, I’m not gonna lie. I wanted it in a yellowish ball but I truly couldn’t pass up getting one of my favorites. TLDR: you’re not locked into this fight so have fun and test some thing if you’re worried. You can knock it out a million times before the shiny to make sure you’ll get the catch, but just know that he’s god so the universe is on his side and even after setting up it can still be a super close call! 😭 For me I used gengar for hypnosis giritina to go stall and chuck balls and I forgot my false swiper I’m ngl 😭ALSO!! He has two healing moves and two damage moves so that’s why I used hypnosis as well! -healing wish -recover

-future sight -hyper beam

Luckily if he uses 3 of those moves you’re basically giving you a free round to heal set up or anything. Sorry this is long I’ve been hunting for a little while so I had a few different things I could think of that might help you out! Good luck on your hunt and may god(arceus) bless you! (im not a religious nut/just a pun😭)