To prevent non-specific staining, it's necessary to prolong the time and increase the times of washing steps. Generally, it's better to be 3 min *3 for the washing before primary antibody incubation, and 5 min *5 for the washing after primary antibody incubation.
Note: Sections should be washed alone to prevent the cross-linking reactions. Make sure not to flush the tissue sections off the slides. Make sure there are appropriate ion intensity and pH in the antibody diluents. ( a relative neutral pH 7-8 and a low ion intensity)