polishing all depends on what you want to polish out (i.e. light scratches, deep scratches, etc).
mothers is good only if you already have a pretty smooth surface. it gives that really good shine. it is more of a finishing product.
for the heavy stuff you will have to move up to either white, brown or black rouge sticks. use this with a buffing wheel.
for even more heavy stuff you will have to move up to steel wool or wet sandpaper. start with a coarse grit and work your way down to a real fine. then you will have to go to the rouges then finish with mothers or similar.
since you are talking about your exhaust pipe. i assume its not too bad a condition. you may just need to get a buff for your drill (lowes) and some rouge sticks (lowes). take it easy then finish with mothers to get the fine scratches out and make it shine.