Not done it myself but the 3 processes usually mentioned to reduce bubbles are:

1. Pouring the final mixture into another pot with a sealed hole near the bottom (e.g. duct tape), then opening the hole and pouring from the lowest part of the mixture, leaving the bubbles near the surface.

2. Once poured into the moat on the frame, flashing over any remaining bubbles with a hot air gun.

3. Not stressing over the odd bubble or two which gets trapped unnoticed.