I'm using Dremel 3000 along with a diamond wheel which is not cheap either at around 20EUR. It does the trick for about 30-40cm and then goes dull. It only cuts when the dremel is at it's highest setting. Anything less and it barely scratches the surface. It seems as if when the resin is heated while cutting, it sticks on the wheel and dulls it. I don't know if that's whats happening but I can see that the dimond wheel is covered with thick black stuff. I can sand it down with some abrasive paper but that doesn't seem to improve anything. Can anybody help me with that? Any methods for cleaning/sharpening the diamond wheel? 

Yep I do love my perma-grit disks! work like a charm, do not get clogged either! I use a flexi-shaft on a regular dremmel.

To get into tight sections I use some of dremmel's own tungsten carbide accessories. Also great.

cheers