I remove the mesh corona grid off the charger frame, and place it on a clean sheet of paper.
I then use a scottbrite scour pad ,(the same you use to wash the dishes with). I place a small amount of alcohol (metho) on the scour pad and literally scrub the mesh grid going one direction away from my left hand that is holding the grid. Do not scrub to hard that you bend the grid.

If you look closely at the grid before you start you will see a dull luster dirty shine all over the grid. It is this toner/dirt and muck that you want to scrub off the grid. As you scrub you will notice the dull luster will turn to a bright shine. You then know you have removed all the insulated type dirt/toner crap off the grid. The copies should then return to full black density as you have full charge returning to the drum. The same with the single grid wire or charge comb. I use metho and scour pad wrapped over a thin steel ruler to scrub clean the charge comb.

You can use your spring hook to clean the single corona wires. You will notice as you scrub the corona wire will return to a bright shine. If you angle the corona up to the light to get the light to reflect off the corona wire, you can see exactly where the wire is clean and were it is dirty.