Liquid under glass when pressing hard, and how to remove dust

I'm starting a small repair business and I'm having 2 repair issues I'd like to get some help with, please. I have this issue when replacing just the glass and sealing it with double sided tape.

1) I've been using the process outlines here and have notice an issue were if I press firmly on the screen I get whats like oil under the screen however it immediately fades once I release the pressure. How can I stop this from happening?

2) It is very challenging cleaning the glass/lcd and getting it dust/streak free. Currently I use a combination of: microfiber cloth, prepackaged/moistened lens cleaner, can of compressed air. Does anyone have any tips for making this part easier?