As i found......
Glitch on Grey, you can have unlimited red book by accept Grey quest and take red book and delete quest and repeat.
Grey's staff Can be use as fuel for furnace(1 item at time, i saw NEI though).
You can have Grey staff and Glamdring(during attack action) by disarm stuff. Even already disarm staff off, during attack action Grey staff will respawn in other hand this time disarm will make grey drop Glamdring grey other hand staff will gone too but not drop.
Grey can be hit by other thing, even did't does damage and grey will rush that player(or mob) to kill it, you can use other mod like Cho Quest hookshot make Grey stick to you to make you keep safe???
If Grey have targer to kill, grey will chase until that targer died otherwise grey will not disappear.
Even Grey is near impossible to kill on survival mode, MF2 cogwork can hurt Grey, Cho Quest element also can damage Grey. all that 2 thing can kill grey in survival mode.
Ok that's i found, good luck try you own. or research.
Edit: Also you basic have unlimited staff and glamdring if you keep disarm grey when come out.