A bit more info may be required:

Sorry, no pics of set-up Chris, but will likely run another part this week. Stack was two plys of 200g twill backed with one of 450g. This was topped with peel-ply and EC mesh which, I believe, is medium flow. 

There is a note in that video that the formula for GC50 has been changed and acetone no longer works to make it tacky.

Brian.

Yes the formulation changed meaning acetone does not activate it in the same way as before.  Acetone could well end up attacking any area that is not fully cured which would make things worse if you have holes in the gelcoat when it comes to infusion.

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant

Doh! That'll teach me to pay closer attention. Thanks gents, glad I raised it now rather than just going round in circles looking for an solution