At least epoxy it.  You wouldn't want water to get through scratched paint and under existing glass. You wouldn't want a heavy paddler to crack the normally thin plywood getting out without some epoxy strength. (experience)  But yes paint will seal the wood. Boats were that way for a long time. They likely had thicker coaming rings though than the typical thin plywood/epoxy composite rim.

If the coaming is mulitple small pieces vertically placed (typically a stripper) to a rim cap you must glass it.

glass the rim.

they actually break pretty easily without glass unless it is a thick rim or well backed up by a fillet on the outside of the riser.  glassing also helps you ensure you actually have the epoxy there that is needed to seal it.  frankly, its not much work compared to just trying to epoxy it.

all the rest sounds fine.  just do a good inspection to ensure no gaps or scrapes in the epoxy that would let the water touch the wood and you are good to go.

h

   Agree with the suggestions to glass the rim.  I did not glass it on my Ch 17LT (directions did not call for it) and it ended up getting significant cosmetic damage when I rolled the boat in the surf.  I glassed the rim on my other boats and they have held up much better.

As for paint, if you live in a hot climate like here in FL you may not want to paint the rim black.  A lighter collor will be much cooler when you touch it.

If you are partial to the bright look, you could always cut/plane/sand the old rim off and add a new one.  Personally, I like the look of varnished sapelle. 

When coating the rim with epoxy, you could add some  graphite to the mix for the Matt black look.