If you're determined to try - and Poser got where it is today by people trying impossible things - here's a couple of tips.

You don't need a greenscreen in Poser. If you render out your animation as a series of still images in .PNG or .TIFF format, they'll automatically have a transparent background. Premiere should be able to import these without a problem.

Poser renders tend to be quite low-contrast anyway, so you've got a head-start.

Experiment with higher-than-normal motion blur settings. Camcorder footage tends to blur movement quite a lot.

Instead of trying to hide the CGI/video difference, could you emphasise it? Think about Matrix Revolutions, where the two guys are rolling round fighting in the mud, and suddenly there's this long, slo-mo CGI shot of a fist hitting a face.

Do you have Poser 6? If so, you can experiment with IBL lighting. It shines a diffuse, multi-tinted light onto your models, making them look more realistic.