I pull vacuum and dump it multiple times at the beginning to reduce the foaming. After it settles down, and no longer foams up, I let it pull for about 3 hours, then dump the vacuum, and re apply vac. If what I call champagne bubbles, (they are small, just like if your looking at a fresh glass of champagne) are slow to start, and very minimal, I dump the vac, and let it sit overnight. At least 24 hours. Making sure there is plenty of liquid above the weight. It will absorb quite a bit over night. Then I pull them, dry them off, wrap in foil, and cure. Been following this procedure for some time and have had great results.
Been doing this for a couple years, and I have never seen any of my blanks, where they did not produce the small champagne bubbles. So if your down to them, I don't think you have to worry.