For sanding: I use these 240 grit (and finer) cylinders. You can buy the basic version on ebay and amazon very cheaply (£2-4 each).
I think they're designed for wood and metal and you do have to be careful with them.
Not because they will hurt you - despite the speed of the buffing machine your hands are fairly safe.
But the sanding 'mops' will chew through the surface of your polymer item before you realise it. This is particularly true of anything that consists of base clay with a veneer of patterned clay over the top. I've lost count of the number of items I've ruined by sanding through to the base clay, thus ruining the item.
The worst thing about this tendency to ruin items is that it always happens at the VERY end of the making process, so it represents a huge amount of wasted effort...
There's a great supplier called Molderoda or 'Polishing Jewellery' and their 'Ask Amy' service is very helpful. It was through Amy I discovered these nylon jeweller's finishing wheels, which are great for the initial sanding of most larger pieces.