Or, you can use a punch/screwdriver and hammer.

Use the proper tool if you can. Most hardware or tool shops will sell some sort of C spanner that will do the job effectively, time after time.

Sorry, but I hate having to try and adjust anything that's been butchered by the previous owner/mechanic/thug. MC28 rear wheel hubs are a great example of where screwdrivers have been used instead of the proper (not expensive) tool.