Our group run shields as soak and below is how we run it.
Any ship with shields has shield points instead of Setback dice applied to their attackers. The shield points are calculated by adding the ships Strain Threshold to its Silhouette, and are ablative. The ship will automatically regain shields at a rate equal to the defence rating for that quadrant as long as the shields are still up. Additionally the ships crew can attempt to reinforce the shields integrity by making a Mechanics roll versus a difficulty based on the current state of the shields. If the ship has lost less than half its shield points then the difficulty is Easy, if it has lost more than half but the shields are still up then the difficulty is Average, and if the shields have been collapsed then the difficulty is Hard. Each success on this roll restores the ships defence in shield points.
Due to the fact of shields are soak in these rules we ignore Armour. The reason for the calculation we use is to stop shields becoming OP. I did a few basic runs using varying the calculations with multiplications of Defence as well as others but no other versions worked. For freighters their shields were too low but for capital ships their shields become way to high, which would just make space combat pointless as it would then become a question of big guns, bigger shields. I tried to work the system so that it achieves something close to the movies.