If you cant get inside and it's not in need of structral repair.
The way I fixed the cracks at the back of daggerwells in the past was I got one of those old fluffy pink bedspreads your granny used, the ones that had a smooth section about 3 cm then a fluffy section about 2cm. Shape a stick a bit narrower than the width of the daggerwell then wrap a piece of the bedcloth around it a few times until it slides snuggly in the well. I mixed up a standard wesystem just to wet out the area, then made a stiff wesystem with heaps of mycrofibres in it. The cloth will carry a lot of the mix and as you rub it up and down it will force the mix into the hole. Re make your stick with fresh cloth and use it to keep smoothing out any drips and to clean up where you dont need resin. That will get you floating.
regards