: I have just finished laying the glass and epoxy on the hull of my yak. I am a
: bit unclear as to how to best deal with the frayed bits around the
: football on the bottom. I assume that cabinet scraper or sandpaper will
: work best but which grit to use and do I do it before or after my fill
: coats?

I use a paint scraper, any of those pictured below will do the job. This lets you work on removing just the offending strand without sanding the surround glass.

If you want to avoid the strands use masking tape to define the edge of the football. Lay the glass over the tape and wet it out normally. Let the resin set up so that it is somewhat leathery then use a utility knife to trim the glass just beyond the tape. Peel up the tape to remove the raggedy strands.

Use good quality blue masking tape and a sharp knife. You will need to do the glassing over several days to let the previous layer set up hard so when you trim you are only cutting the new layer.