Brakes stop you by generating friction as pressure is applied. If you polish it - especially with things such as polish, wax etc. - you reduce friction. There is no way polishing your brake surface will somehow magically make the brakes work better. Maybe if you haven't ridden the bike and you "test" it by applying the brake without moving the bike. In that case, I can imagine that something feels sticky.

The mentioned product (Mother's mag and aluminium polish) is for the rims (on cars and motorcycles) and not for the brake rotors on the mentioned vehicle. I know your rims are rims, but with rim brakes they are also the rotor.