Many maps have grid lines drawn on them. There should be an easy way to mark where two lines cross and specify the lat/long of that point to georeference it. On some maps, just marking all the grid points would be all that is needed, and would be much easier than matching up map features. Some maps (especially older ones) might have inaccurate lines and need corrections from there, but using the lines would still be a big help to get them started. I've also seen a couple maps where the grid lines were almost the only usable details.