you will need a sturdy tooth brush, cotton tips, leather cleaner (ph balanced), leather conditioner, soft cotton towels and lots of patience!!!
1-clean the whole seat with leather cleaner (ph Balanced, very important!)
2- with the tooth brush and soft pressure go all around the stiches, follow with cooton towel.
3- apply leather conditioner, let it sit for about 10:00 min
4-rub it off the excess with cotton towel to bring some luster up, use the cotton tips to clean around and top of the stiches.
use the same procedure at least once a month, and have the leather intirior finishings detailed twice a year. good luck!