I fill my bathtub with warm water and 1 cup of ammonia and 1/4 cup of dish soap. Put the blinds in and let them soak for an hour. Then rinse and rehang.
I hope this is what you need: https://www.youtube.com/watch?v=iL5rd6-X4pY
If they are wooden the old fashion way works best. A soft cloth with a mild detergent and wipe over gently. For the vertical blinds I put mine in the bathtub and scrub with a soft scrubbing brush then hang them on the washing line to dry. You can also hang them damp on a hot day.
Hi Sophia: I use warm water and some Dawn in a bucket, maybe a splash of vinegar, and have a bucket of clean warm water, too. I put an old, thick, cotton sock on my hand, put it in the soapy water, wring it out and do the top and bottom slat at the same time and in between the strings and that little edge that sticks out. Once they are all done, I get another old, thick sock and wipe them again with the clean water and squeeze the sock so it's not dripping. It only takes a flash, and you can look outside at the same time and watch the birds:) And, this is a good use for that one sock without a match:) Good luck