Ignore all the advice saying check if the servos move the same speed - if loaded differently they will not move at the same speed even if identical, so this is not useful.
#2 and #8 are definitely the correct approach - command them frequently in small steps so they are never allowed to be far from the desired position - you have to ensure you don't try to move them faster than their natural speed under load as they can only follow commands within their physical limitations.
In other words do position control on a frequent basis, not rely on any inbuilt speed control (which doesn't exist in normal servos).