Is resurfacing the brake pads in disc brakes (hydraulic or mechanical) necessary? If so, what would you use to do this - medium sandpaper?
I spoke to one mechanic while shopping for a bike, who suggested resurfacing on a monthly basis...
You've met a mechanic that either wants you to buy more brake pads from his/her shop or doesn't know what he/she is doing. There's really no good reason to resurface your disc brake pads, let alone on a monthly basis. All that's doing is decreasing the life of your pads and temporarily decreasing your braking power until your pads bed back into the rotors.