My experience with bubbling has been that the viscosity of the ink is   
most critical.
Mixing will always inject air as does forcing the ink through a screen.
The key factors are; how viscous is the ink (It's hard to get bubbles out   
of peanut butter.),
how thick is your coating (thicker coatings are harder to get the bubbles   
back out of), and how long do you allow product to sit for de-bubbling   
before tack-dry at what temperature.
We had a rash of bubbling problems recently when one of our two suppliers   
sent in some thicker than normal ink.  We're looking at incoming   
inspection for viscosity.