I have a basically completely new brake system, which means the lines were empty. I did bench bleed my master cylinder. I am getting air bubbles hours later. I have to be doing something wrong? I don’t think it should be taking this long. I have tried alternating sides to get the air out. This is for the rear drums.

Help me oppo. Most info is for when small stuff is being repaired.

Edit:I may be missing this BS tool:

https://www.performanceonline.com/GM-Combination-Proportioning-Valve-Bleed-Tool-AC-Delco/