Mike - Prior posts recommend to seal the deck prior to filling cracks or to tape off the area next to the fill area to prevent blotching. As well to use wood flour lighter than the color you are filling because epoxy will darken it when mixed. I mixed in pine wood flour to lighten WRC.

The sand paper on tape or webbing sounds like a great idea for the sides of the coming under the lip. This will work in the front and rear corners, but you probably won't have enough pressure on the sides and back to be effective because of the flat shape. I just took a piece of stripping, removed the b&c leaving it 1/2 " x 1/4" a foot long and wrapped it with 60 grit paper. Fold the edges of the paper as you wrap it and you will have 4 nice sharp edges to get the sides of the coming as well as under the lip. By using wood you can use the freehand to create extra pressure where you need it to improve your effectiveness.

I did some major veneering on my double (picture attached) and I sealed the deck first prior to veneering. Then re-epoxy two more times to fill in the edges of the veneer prior to glassing to eliminate bubbles. (I had only 1 tiny bubble of course right on the top of the deck.

Good luck on the remainder of your project.

Dave - The Kayakaholic