Thanks for the great summary and testing. I have been making a lot of Milcery rank curry, but am not that organized in recording my numbers. I'll try to get better about that with my next round.
I didn't realize that Pokemon's levels might have an effect ... that's an interesting initial result. I'll be using a team of level 100 max friendship Pokemon from now on.
I pulled the numbers out of the initial YouTube video by だま / Dama that I found. Dama’s results below are [the number of Pokemon attracted] / [the total number of curries made at that rank]. Of course, we don’t have all the details (i.e., the level of his Pokemon, their friendship level), so take this with a grain of salt. But it looks like he did a lot of tests.
Milcery: 1056/7063 (14%)
Copperajah: 23/300 (8%)
Charizard: didn’t test (the video notes it’s too difficult :))
If you are interested in Curry Mark Shiny hunt testing, here are some tips that might help:
Obtainable Pokemon by route/area: Dama shared this list on on his Twitter, which is the only list like this that I've seen so far (https://twitter.com/monst_dama/status/1236942855538487296?s=21). I have not verified the accuracy of this list, however, from my tests on Route 1, Route 4, Route 10 (Near station), and Glimwood Tangle, it seems accurate so far. Pick a Pokemon you'd like to hunt for but keep in mind theSLAYER's theory about Curry Mark encounter rates being the reverse of that route's normal encounter rates.
Easy Milcery curry: (note that theSLAYER's initial tests indicate higher ranks of curry bring better encounters)
You don’t even need to touch the controller to get Milcery rank:2,200 ingredient (Smoke-Poke Tail, Large Leek, Fancy Apple, Boiled Egg, Fruit Bunch, Moomoo Cheese) + 10 berries from Wedgehust Berry Grocer.
If you’re willing to button-mash (or use a Pro controller): 400 ingredient + 10 berries
Stating the obvious:
This is sort of stating the obvious, but it’s something I didn’t consider at first. For the Pokemon in your camp, pick small Pokemon that are easy to see around. For example, I had a Coalossal on my team during my initial testing and while Coalossal is a favorite of mine, he kept obscuring the screen and telling him to go play and move took extra time for checking if there was a Curry Mark Pokemon behind him. Pokemon with low profiles (Eevee, Yamper, Pikachu, etc.) or that are easy to see around are your best bet for quick check.
If a Curry Mark Pokemon appears, you shouldn't have to adjust your game's camera to see it. You don't have to look alllll the way to the left of your camp and all the way to the right of your camp or up or down to see the Pokemon. Keep in mind if you have large Pokemon in your camp, they might be obscuring the Curry Mark Pokemon.
If you attract a Pokemon to your camp, be very careful about avoiding the B button. When a Pokemon comes to your camp, the dialogue “Oh…? <This Pokemon> has come to your camp. <Pokemon> seems to want to be with you. Do you want to add it to your team?” If you hit B, that will select “No” and the Pokemon will go back into the wild. There’s no confirmation screen or “are you sure” sort of dialogue if you say no. Once the Curry Mark Pokemon is gone, it’s gone.
For the point "It appears that encounter rates for curry encounters are reversed.": Including my Curry Mark encounters and the encounter rate from Bulbapedia below.
From my Route 4 testing (shared this in Discord yesterday -- nothing new):
8 Ferroseed (1%)
3 Joltik (10%)
3 Milcery (20%)
2 Budew (4%)
1 Wooloo (25%)
From my Route 10 (near station) testing:
12 Darumaka (5%)
10 Snom (10%)
8 Klang (30%)
5 Rhydon (25%)
5 Vanillish (30%)
Crazy question: Could having Curry Mark Pokemon hanging out in your camp maybe increase the odds? I don't think so because I haven't heard anything about the other Marks having other effects outside of adding a title to the Pokemon's name, but if I have the time (haha) to max out the friendship on a team of Curry Mark mons, I might try this too.
Other Shiny “proof” clips: I can’t vouch if these were hacked or using CFW, but they show what a shiny Pokemon looks like in Camp. Similar to the Dama video that's already linked to.