| Did you look at the "Back to Basics" thread? It might help you off to start with.
As for intricate thaings like gear legs, I used to do a lot by what they call "Adzing", which is basically dragging your sharp knife over the raised edge of the seam until it is flat. You then need to finish off with a fine wet and dry or, as you say, a buffer.
One thing I do a lot of and that is glue various bits of wet and dry paper to things like lolipop sticks and coffee stirrers. You can trim them to any shape and hence generate some nice fine sanding tools. They don't last long but what's a coffee stirrer?
I usually find with little fiddly bits that holding them by hand is usually the best because tools can be a bit damaging if you are not careful.
As for painting, most small bits are best removed from the sprue, then reglued to a bit of sprue on a spot that won't be seen on the completed part, before painting. Then when you remove it finally the unpainted bit is hidden. Take a pilot, cut him off the sprue, dress him up and then glue him by the bottom of his foot to a peice of sprue. I usually stretch a piece then cut it at just the right diameter along the taper to give me the best fit. Then paint him up and finally remove him from the sprue. The unpainted bit is under his foot then so well out of sight.
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“Dirty British coaster with a salt-caked smoke stack, Butting through the Channel in the mad March days" | 
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