How to deal with the bubbles during the mixing process?

It depends on your practical situation. Firstly you can deal the mixture with a vacuumizer if you have one; If no such machine, you can reduce the mixing ratio of the hardener from 5% to 2%-3%, then in the prior period of the reaction of the mixture will be slower, then the air in the mixture will exhaust by itself for a longer curing time to release the bubble.