All the above. No seriously, depending on the degree of boo boo you can use either of your choices. The scraper is really nice for minor "shaving" off of imperfections, sanding is next up the scale and finally grinding for the really nasty stuff. Lots of people don't start with a course enough grit and end up sanding waves into their part, don't be afraid to be aggressive, just don't sand to or through the glass.

I have used a rotary tool (Dremmel like) with a small sanding drum to grind off high spots. I now have a set of furnuture scrapers, including one with curves, that can be useful. Sandpaper on a dowel can be used too. I'm on the tail end of my first build and did lots of "learning" along the way, including dealing with some less than perfect fillets. Now on to a WD 10, EP Pram (might as well add a WD 12 at some point) and finally a PocketShip.

And yes, for the runs, use a scraper. I actually grind off the tops first if they are horrendous (rotary tool) and then go at them them with the scraper. If the runs are on top of the final coat of epoxy, you could use an ROS, but I would scrape first.

Thanks for the replies. The problems aren't on top of the final coat; they're the initial tack welds. I just think I need to cut them down somehow before I fillet and epoxy.

I have a Dremel, and I think I'll try that first.

Good luck with it. I find that if I just take the tops off with the rotary tool, a scraper does a very good job finishing it off.

Oops.. I was thinking of runs when I mentioned the scrper. For the "tack welds" the rotary tool should do just fine.