Open the blinds fully before removing them from their window tracking and placing them in the bathtub. If you don't have a bathtub, a child's plastic pool works just as well.
Fill the bathtub with warm water about three quarters of the way full or enough to completely cover the blinds.
Add 1 gallon of white vinegar to the bathwater and swish it around with your hands. The vinegar will corrode the grime on the blinds without eating into the blinds themselves.
Let the blinds soak in the bathwater until the dirt has completely disintegrated. Stir the water to loosen surface dirt from the blinds.
Empty the bathtub and rinse the tub and blinds in cold water. Use the shower or showerhead attachment. Cleaning your bathtub fully after finishing with the blinds is highly recommended.
Allow blinds to dry outside on a large clean towel in the summertime. During cold weather, pat dry blinds using a soft clean towel before hanging back on the window.
Dust blinds weekly to help maintain the blinds and prevent the build up of moisture and grime. An old sock on the end of a broom handle is a good way to get between the slats.