By using one of them wide brushes with sparsely populated wire needles, with plastic beads on their ends. Feels good in the scalp too. And brush while your hair is still damp.
I go to one of those garage places that has the pressure washer thing you put coins into. Turn the dials through the stages (water, soap, etc) and spray, brush, and rinse.
How do you check if your steak is cooked how you like it (sight, feel, temp, bite it)?