Destiny 2: Fastest Way to Upgrade EDZ Seraph Bunker

Upgrading the Seraph Bunkers is a confusing mess.  Here is the fastest way to upgrade the Destiny 2 Seraph Bunkers. 

Last season the Obelisks had a relatively straightforward upgrade path.   The upgrade path for Seraph Bunkers is not quite so intuitive and to many players I have talked to it seems very, very slow.     It is slower than the Obelisk upgrades, but once you know the path to take it isn't as daunting a task as it seems to be at first glance. 

Most Important!  Do the Bounties.  
This is the same as the Obelisks.   Do every bounty that you can do on every character.   This is a lot of grinding, but if you can gut through it you will be able to upgrade the EDZ Seraph Bunker in week 1.   This is the fastest way to go. 

Remember your upgrades are shared between characters, so you can triple the speed by playing all three characters. 

There is also an unlock for a repeatable bounty from Rasputin.  It returns 12 bits each time and is repeatable.  

The EDZ tower event (which is a lot of fun) gives you 6 bits if you succeed and 4 if you fail. 

You can also get an upgrade that gives bits for running regular content.  I haven't used it enough to know if it gives much, but something is better than nothing when you are trying to go as fast as you can.