The tools usually used in post work of Poser renders are:

1. smudge to hide crumpled mesh at joints
2. liquify to get rid of shoulder bulges
   3 shadow/highlight or levels adjustment to adjust the perceived value range
3. noise or a third-party filter to simulate photographic grain in some cases
4. I also find I use Photoshop to de-saturate renders as it is easier than doing it with lighting or nodes.

Can't tell you about editing animation frames... are animation renders outputted as flash files or can the frames be saved out individually? My only advise for animating and Poser is start with low-res figures such as the Poser 4 figures so you have a reasonable render time when you are learning. I used to just output the un-rendered preview displays to paint over in Photoshop back in the Poser 4 days.

PSP actually has better "movie" making tools than Photoshop I think.