Tumbling Nightmare

[Signature Silver]

Hi all,

I posted on here last week some time asking for advice about whether or not to buy a Dremel to help with polishing my fingerprint jewellery. Most of the replies i got seemed to suggest I didnt need one and to use a Tumbler. I have got the tumbler back out of the cupboard again having not been happy with it when i've used it previously. I fired my pieces in the kiln yesterday and put them in the Tumbler last night for about 2 hours and I am still not happy with the finish on them. I have attached a photo so you can see what i mean. They are nice and shiny but a little mottled on the backs which i just cant live with. How do I get them smooth?
Did i not have them in the tumbler long enough or should i now be sanding them by hand or something? I thought the tumbler was supposed to do most of this for me?