1) Even some free stop-motion programs have onionskinning. Seek ‘em out.
2) To loosen legs, get some light machine oil (eg, for sewing machines) and rub it on the joints with a paper tissue. This frees them up.
3) […]

I’ve seen this done in a few brickfilms, but I’ve never seen it done well. Down at Lego scale, hand-drawn images look very crude. If you have access to an inkjet printer, try and get hold of some decal sheets — […]

Excellent! I like restricted colour brickfilms, because they seem much more integrated. Nice little story, good animation too…

Here is another technique:
http://bricktrick.de/index-e-bafran.php
The English is a bit peculiar, as it’s translated from German, but it’s quite a simple technique, and the program is free.

Some great advice. Thanks for posting.