i have used the "cutting away scraping area" technique in the past. usually with an exacto knife, trying to keep the section you cut away in the same basic shape as it started. the only thing is that you end up with a lrger space and somtimes that looks wierd, especialy on arms. the other problem you may run into with this is by removing sections from the joint you may losen the joint, so now your limbs are floppy!
the thin paint technique has worked best for me. i always try to chose parts colored as close as possible to the color i plan on painting it, if possible! or chosing a joint that may be the color of some weathering you may do. it narrows down the amount of parts you have to select from, but allows you to get the disiered articulation. it is up to you which you want more though, articulation or unchipped paint.
another thing i have yet to try but have been wanting to do on say a shoulder joint or somthing, is try to make a super thin layer of sculpy to fit over the moving part of the joint and paint that. but that may restrict movement to, like i said i still haven't tried it, just somthing i was thinking of!
hope your painting goes well and can't wait to see more of your custom's!