you have a couple of troubles you will have to over come when trying to get a duller finish on a polished item
it will depend on the item you are trying to work on - curved items may look different to a flat surface when polished due to the light being reflected, and so if you are sanding down you need to s=work out which way to sand and what little lines it will leave - on a hub it might be better to follow the curve instead of going across it !
As for chemicals - there are different methods and stuff to use !
most will dull the polish down but will also darken down the colour from what it used to be like as a factory finish
i have found that cillit bang can work well but can be a bit harsh compared to CIF (stainless steal cleaner) which if only used in a short time can give a better finish and doesn't darken down the item straight away - but if left in a long time it can eat into the alloy and leave pitting (good for making it look pre 80's )
Oven pride will darken down items but can be patchy in place's as it is not fully submerged in the stuff (stronger in a bag instead of brushing )
Silver dip can work but it is strong and is only needed to be dipped in quick and never left !
you can also use the kitchen sponge with the green scrubbing pad - a fresh sponge will be more harsh and leave bigger lines - one that has been used and soften down will work best - a well used one can start to polish more than dull down
it will be a case of finding some thing that is similar to the item that you need doing, and give it a test out - take photo's so you know for next time (or you can forget and use the wrong stuff next time and get a wrong finish)
so test out first is my experience
cheers B