[OSM-newbies] National park boundaries

[swanilli]

I have been trying to tidy up some Australian national park boundaries
and was wondering if there was a simple way to do it.

What I have is this:

1.  Administrative boundaries provided by a government agency. I take
these as being accurate as they are quite detailed.
2.  Park boundaries apparently drawn roughly based on Yahoo imagery.
3.  Coastline also apparently drawn roughly based on Yahoo imagery.

For most of the park boundary all 3 should be identical but are not. I
have been tidying them up but it is a long and tedious process
involving moving thousands of nodes. I have tried copying and pasting
but this is messy too. The whole thing is further complicated by the
2000 node limit in JOSM which means that they need to be split and
made parts of a multipolygon.

Does anyone have an easy, unmessy, solution?