After trying various ginding tools I have found one that ginds these seams like warm knife through butter. It cuts so fast sometimes you have to be careful with the pressure you put on the tool [img]tongue.gif[/img]
I'm a woodworker but don't do any carving so I never bought any of this stuff. While shopping at our local Woodcraft store I noticed a Foredom flexible shaft carver. It uses a tungsten carbide burr and has a standard 1/4" shaft. I bought one and chucked it in my die grinder and layed into a seam. WOW my gelcoat disapeared!
If you don't have a Woodcraft local to you the link is www.woodcraft.com
and here's a picture of a burr. Mine is silver and is longer than the H item pictured but you get the idea. Just be careful because it cuts extremely fast. I just love using the right tool for the job!