youre ment to take off the disk? some people just spray it aswell as the brakes will take it off in time but thats a bit bodge tbh
just remove your wheel dude its simple to do, undo caliper bolts take caliper off its a bit of a tight squeeze between the disc and the wheel rim but it will come out, remove the bolt that holds the wheel in place then undo the 10mm bolts that hold the disc to the wheel