Are you sure it's not just cracks in the gel coat? My understanding is that the acute angle and thick buildup of gelcoat in the mold makes that part prone to gel coat cracking. Anyway mine sure has a lot of them. Which I'm about to start grinding on if the weather holds.
I also do have a real crack in the toe rail from some long-ago impact. When I first bought the boat, I slathered it over inside and out with 5200 and forgot about it for the next seven years. But now it's time to get real about it.
So, the toe rail is an inverted U shape that's part of the deck. You can access it from inside the "ducts." Except in some places it's open and in others, the open side has been glassed over. Or just (apparently) some resin-saturated matting was stuffed into it. (This cleverly prevents access to the genoa track bolts.)
Let's see if I can find some pics from my original survey.
Actual toe-rail crack:
View attachment 25411
The developing plan is to use a can opener or dremel tool to open up the gel coat cracks and chips, then fill with thickened epoxy as per the West systems manual. For the crack, i think the best course may be to patch it from the inside. Building up any more material on the outside would interfere with the genoa track. One idea I'm toying with is to shape a wedge of hardwood about three times as long as the crack to fill the "U" and epoxy it into place. Then drill all the way through it for new genoa track fasteners. Ah - note the adjacent scupper which... scuppers that plan. But something like that.
When all the various booboos on the deck are fixed, I'll paint the whole thing with a two-part polyurethane. Probably next March or so.