I haven't tried polishing reflectors that I have. I bought a DIY kit to build the hood for my 4 foot tank. They came with some really fancy reflectors that the company claims are much more effective than other reflectors, because of the way they are bent and they are more shinny. There must be something special about them since they made up about half the cost of the kit. That hood does light better than any of similar market hoods I've seen. I'm not sure if it is the actual hood or the bulbs that make the difference.
The reflectors are very mirror like.