Made an account after lurking for months, to post that I had a very positive experience conditioning my black leather case with mink oil.
Having done extensive research, I'm aware this is not the absolute best conditioning solution available however it's been tried and tested for decades on leather products and is easily obtained locally from leather and shoe stores.
The jist of the proper application procedure is:
1. Clean the case with a fine cloth rag - you just wanna make sure there's no crap like lint etc on the case.
2. Again, using a fine cloth rag, rub a thin even coat of mink oil on the leather. I would avoid the inner piece that hugs the iPhone metal frame as you don't want this grease on the microfiber linking in any way, shape or form.
Note: I used the case for three weeks before applying three thin coats of mink oil, allowing 15 minutes in between.
3. Allow the mink oil 12 hours to absorb fully; store in a cool dry place. I just put mine back in the box, opened slightly to allow air circulation
4. Wipe case lightly with fine cloth rag - I feel this isn't needed as long as you applied a thin enough coat but it's what the guides say so I'd be shooting you in the foot if I didn't mention it here
I'm very pleased with the end result:
!!DISCLAIMER!! - I've only used the case for a day after the application, you may want to check with me in a couple weeks before trying this on your own case.
-case is GRIPPIER!!! this is the main reason why I did this as during the cold season (Canada - it's still cold AF here) my hands tend to get fairly dry, making my experience with this case a slippery one. I also own the Apple silicone case which scores a 10 for grip whereas the leather variant a 3. After the mink oil application the leather variant scores ~5 to 6 for grip which made a world of difference with my dry hands.
-case texture is more pronounced, the pores stick out a little more. To me it looks more textured and refined.
-no strange odor, although that may dependent on the brand of mink oil used. I used BAJ Mink Oil which you can find online using the following search string in Google:
Pics on Imgur album linked below. I forgot to take before pics!
https://imgur.com/a/VNWn2
As it's impossible to tell whether there is any color difference on the black variant, If I get a bunch of requests to try the same on a lighter colored Apple Leather case that can be arranged - saddle brown appears to be a popular choice.