best advice for BB30?
don't use "grease" its for lubricating bearing races, not fitting metal parts to metal parts
clean shell with iso alcohol
apply good smear of shimano anti-seize around inside of shell where bearing contacts shell, including the metal circlip the bearings sit against
fit quality bearings using press fit tools. more anti-seize on the inside diameter of the bearing where the metal crank axle contacts the bearing
anti-seize on the outside faces of the bearing where the shields sit, before installing crank with torque wrench
for PF30 or OSBB we bond the plastic cups into the frame using low strength epoxy adhesive.
this is after using loctite bearing retainer compound around the inside of the plastic cups where the bearings sit, and pressing the bearings into the plastic cup using correct tools.
Entire assembly then pressed into frame, before epoxy dries fit the crank (using shimano anti-seize between bearings and crank axle, seals) and set to torque, left overnight for epoxy to cure properly.