Thought I might as well share my hand-wash method:
1) Prepare your detergent.
In my case I choose to use the Sugar Cane ‘vintage wash’ enzyme detergent. Other options include: Samurai’s washing powder, Momotaro’s denim liquid, soap flakes, gentle/non-bleach detergent, mild shampoo, etc.
2) Prepare luke-warm water (best not over 40 degrees Celsius), no more than 30L, in an adequately large container.
3) Mix the detergent with water. If you are worried about excessive indigo loss (usually not a problem with Japanese makes), then add a table spoon of salt to help the indigo hold fast (please no sea water, you don’t know what’s in there…). Add jeans & let it sit in the water for ~20 minutes.
After 2 minutes in the water, the enzymes in the ‘vintage wash’ is already starting to take effect – notice the water becoming murky.
4) Wash the jeans – put your hand in and get dirty! Scrub areas that are extra dirty – don’t do it too hard though.
5) Rinse jeans with cold water, ensure all the detergent is washed away!
6) Optional step: if you have denim treatment solutions, such as the Sugar Cane ‘premium care’, use it now. Add the solution to water and soak the jeans in it for 15 minutes, then proceed to drying (do not rinse out the treatment solution).
7) Dry jeans in the shade or in gentle sunlight. During the drying process, apply your choice of leather treatment (the leather sucks up the nutrition best when it is slightly wet).