Yes, flagging (as outlined in this question and goldilocks' answer: Improving link-only answers) is definitely helpful... with one reasonable limitation. If the post already contains the comment that it will be turned community wiki we already have it on the list. Flagging again is not necessary and more or less noise only.
Equally important is to use the opportunity to edit and improve the answers after they have been turned to community wiki.
More important however is now that the next step: actual improvement of the answers by the community. As goldilocks had put it: remember, it does not have to be a major production More often than not just providing a little context could make the answer stand on its own. If nobody ever cares to edit the wikified posts there's little use in proceeding that way.
To this end we've created a chat room which is publicly viewable, to which we add such questions once they've been converted to "community wiki" -- an advantage of which is you can do edits directly, no peer review, with 100 rep:
You won't earn points from the answer (but neither will anyone else, including the original author), however, if you see something you are interested in, reading the link and supplying a brief summary may be a win-win.