No! PCB needs to go on before you strip the blade. The coating acts as a resist layer to the etchant. Also, tape up your exposed edge with some masking tape before you start.
Apply it for about an hour (or until it looks like the etchant is saturated with metal). Rinse and repeat as desired. 2-3 applications should give you a nice deep etch that won't go away. You can neutralize the etchant with Windex. I know, I didn't believe it either, but it works. When you've done all you want to do, rinse with water, spray it with Windex and scrub the area with an old toothbrush / sponge. Rinse clean and then you can get to work on stripping the blade.