62 plate c4 picasso with electronic handbrake and no release button - brake pad renewal

I am about to replace the rear brake pads which I have found a suitable post for but there is still a question about releasing the automatic handbrake first. I note in the handbook there is an emergency release mechanism under the left hand seat and you use a tool supplied in the tool box to pierce a small plug and then wind the tool clockwise to release the electronic handbrake. It says you have to go to a workshop to get the plug replaced but I assume if I use common sense I can plug this small hole with a pen top or something similar to prevent ingress of moisture or grit. Has anyone else used this method when changing the rear pads and is there anything else I should be aware of with this method.

Thanks