Originally Posted by SiXeVeN
Sandblasting... hmmm. That might actually work.
True sandblasting is a bit harsh... and potentially damaging. Most use soda blasting as a more controlled way of removal, and even that can remove gelcoat. Retclt's sandblaster setup could probably do it, just use a gentler medium. At work we use a glass beader to clean parts - another "gentle" sandblaster application.
If you use a "sandblaster" I'd practice at a distance and see how effective it is and whether or not you actually remove material, rather than just dirt and grime.