I believe you are asking something along the lines of: If you have already taken IM boards, is step 2 easy. But this doesn't really make sense. The only reason you'd go back and take that is if you were practicing internationally and wanted to come into the US and do a residency. In which case you would be already certified using another metric of performance than US standards. So that question would be hard to answer. As for an ABIM doc going back and taking Step 2 again, you would have to really enjoy punishing yourself, lol. I can't think of any real, good reason to WANT to do that ABIM. ABIM is hard enough as it is.
I know a couple IMGs who had past residency experience before coming to the US for residency. These people all got 260 plus on CK, and one person even got a 275. (The people I'm referring to are from a variety of specialties: One did a residency in Surgery, one in anesthesiology (she was a practicing anesthesiologist for a couple years), and another did a residency in IM before taking the steps).
So yes, its definitely a bit easier to do well on step 2 CK after taking any boards that require you to know a majority of medicine. Hope this answers your question.