Blish HUD supports launching in tandem with Guild Wars 2 in multiple ways:
Enable stay in tray: Enabling stay in tray will keep Blish HUD running between sessions and it will auto attach to Guild Wars 2 when you launch it. This is the easiest way.
Launch Guild Wars 2 with Blish HUD: If you have stay in tray enabled or launch Blish HUD before the game shows, you can double-click the Blish HUD icon in the tray (or right-click it for more options) to launch to game.
This means the easiest combo is likely to keep stay in tray enabled and then just double-click the Blish HUD icon in the tray anytime you would like to play GW2.
Launch GW2 with Blish HUD: If you create a shortcut to Blish HUD, you can add a launch parameter which will auto-launch GW2.
That means your Blish HUD shortcut will essentially do both jobs for you.
Here is the exact bit added at the end:
The 2 tells it to auto-login. If you prefer it not autologin, you can use: