Hi Steve,
No alternative to elbow grease I'm afraid.
400 - 600 - 800 - 1200 - 1500 wet n dry (don't forget to put some washing up liquid in the water...helps the process along)
...I used the sailboats GRP system (cutting polish designed for boats - which are gel coat f/glass)...works loads better than t-cut and auto products that are designed for paint.
www.sailboats.co.uk - 3G compound, then cutting boat polish, then carnauba wax.
...let me know how you get on...around 50 hrs should do the trick!
ATB
Rich