I believe CSMaclaren - a user here - has a detailed thread on what he tried out when working on a Rubies Supreme helmet. I can't remember what he found to be the best to stick to the ABS and that was flexible enough not to crack when handing the helmet. It's worth checking out some of the WIP threads about this particular helmet.
Frankly, there are some structural things with this helmet that is difficult to fix, but it is possible to work around it and still make it look good. For instance, the eye sockets are way too large for being accurate, and would take a lot of cutting, re-positioning and gluing things back together to fix. It all depends on how much work you want to put into this, or whether you just want to fix the most glaring issues and create a nice looking helmet from that. I have seen several Supremes, where only the minimal fixes were done and they turned out great. You don't have to go all out to create a cool looking helmet, but if you are bitten by the accuracy bug like some of us here are, then all-out could be the thing for you.
The assistance all depends on what you want to do with the helmet. Just fix the most glaring faults or go crazy accurate. Also, some of the wonkiness is accurate, so be careful what you alter. Better to ask first instead of regretting unnecessary fixes later.
Good luck on your quest.
