Furniture, Wood and Cabinetry Finishing - fast drying poly

I am having a lot of trouble with fine bubbles in my polyurethane finish. My first couple of strokes are fine, I don't go over and over them. By the time I am 1/4 of my way across the table, the brush lays down lots of tiny bubbles. This is on the first brush across the area, not the sixth or seventh time in the same place. I am using a china bristle brush. I end up wiping the urethane off with a cloth, so I am ending up with very, very thin coats. Could the problem be the fast drying urethane? Thanks

Usually bubbles are a result of shaking up the poly instead of mixing it with a stir stick. You might try thinning the poly a little.

I am thinning the poly. Started out 50/50, now down to 90/10. Only stir the poly gently, never shake.