I just take a strainer bag and fill it with a handful of compost, I use 2 4" airstones connected to a air pump and let sit at the bottom, also have another pump blowing air through 2 small 1" stones that I put in the strainer bag with the compost itself. Then I hang the bag into the water and aerate.
From my understanding, tea that is foaming is best because you have reached a peak amount of bacteria. The foaming is actually bacteria dying off. When it starts foaming I would use the tea, which is usually 18-32 hours. If you add more air, more bacteria would form because of more oxygen.
Also I belive some teas won't foam because of the oils that are added from certain amendments or liquid fertilizers.
Someone correct me if I am wrong.